Computer security

Computer security is a branch of technology known as information security as applied to computers. The objective of computer security varies and can include protection of information from theft or corruption, or the preservation of availability, as defined in the security policy.

Computer security imposes requirements on computers that are different from most system requirements because they often take the form of constraints on what computers are not supposed to do. This makes computer security particularly challenging because it is hard enough just to make computer programs do everything they are designed to do correctly. Furthermore, negative requirements are deceptively complicated to satisfy and require exhaustive testing to verify, which is impractical for most computer programs. Computer security provides a technical strategy to convert negative requirements to positive enforceable rules. For this reason, computer security is often more technical and mathematical than some computer science fields.

Typical approaches to improving computer security (in approximate order of strength) can include the following:

• Physically limit access to computers to only those who will not compromise security.
• Hardware mechanisms that impose rules on computer programs, thus avoiding depending on computer programs for computer security.
• Operating system mechanisms that impose rules on programs to avoid trusting computer programs.
• Programming strategies to make computer programs dependable and resist subversion.

Hardware mechanisms that protect computers and data

Hardware based or assisted computer security offers an alternative to software-only computer security. Devices such as dongles may be considered more secure to the physical access required in order to be compromised.

While many software based security solutions encrypt the data to prevent data from being stolen, a malicious program may corrupt the data in order to make it unrecoverable or unusable. Hardware-based security solutions can prevent read and write access to data and hence offers very strong protection against tampering.

Secure operating systems

One use of the term computer security refers to technology to implement a secure operating system. Much of this technology is based on science developed in the 1980s and used to produce what may be some of the most impenetrable operating systems ever. Though still valid, the technology is in limited use today, primarily because it imposes some changes to system management and also because it is not widely understood. Such ultra-strong secure operating systems are based on operating system kernel technology that can guarantee that certain security policies are absolutely enforced in an operating environment. An example of such a Computer security policy is the Bell-LaPadula model. The strategy is based on a coupling of special microprocessor hardware features, often involving the memory management unit, to a special correctly implemented operating system kernel. This forms the foundation for a secure operating system which, if certain critical parts are designed and implemented correctly, can ensure the absolute impossibility of penetration by hostile elements. This capability is enabled because the configuration not only imposes a security policy, but in theory completely protects itself from corruption. Ordinary operating systems, on the other hand, lack the features that assure this maximal level of security. The design methodology to produce such secure systems is precise, deterministic and logical.

Systems designed with such methodology represent the state of the art of computer security although products using such security are not widely known. In sharp contrast to most kinds of software, they meet specifications with verifiable certainty comparable to specifications for size, weight and power. Secure operating systems designed this way are used primarily to protect national security information, military secrets, and the data of international financial institutions. These are very powerful security tools and very few secure operating systems have been certified at the highest level ( to operate over the range of "Top Secret" to "unclassified" (including Honeywell SCOMP, USAF SACDIN, NSA Blacker and Boeing MLS LAN.) The assurance of security depends not only on the soundness of the design strategy, but also on the assurance of correctness of the implementation, and therefore there are degrees of security strength defined for COMPUSEC. The Common Criteria quantifies security strength of products in terms of two components, security functionality and assurance level (such as EAL levels), and these are specified in a Protection Profile for requirements and a Security Target for product descriptions. None of these ultra-high assurance secure general purpose operating systems have been produced for decades or certified under the Common Criteria.

In USA parlance, the term High Assurance usually suggests the system has the right security functions that are implemented robustly enough to protect DoD and DoE classified information. Medium assurance suggests it can protect less valuable information, such as income tax information. Secure operating systems designed to meet medium robustness levels of security functionality and assurance have seen wider use within both government and commercial markets. Medium robust systems may provide the same security functions as high assurance secure operating systems but do so at a lower assurance level (such as Common Criteria levels EAL4 or EAL5). Lower levels mean we can be less certain that the security functions are implemented flawlessly, and therefore less dependable. These systems are found in use on web servers, guards, database servers, and management hosts and are used not only to protect the data stored on these systems but also to provide a high level of protection for network connections and routing services.

Security architecture

Security Architecture can be defined as the design artifacts that describe how the security controls (security countermeasures) are positioned, and how they relate to the overall information technology architecture. These controls serve the purpose to maintain the system's quality attributes, among them confidentiality, integrity, availability, accountability and assurance."In simpler words, a security architecture is the plan that shows where security measures need to be placed. If the plan describes a specific solution then, prior to building such a plan, one would make a risk analysis. If the plan describes a generic high level design (reference architecture) then the plan should be based on a threat analysis.

Security by design

The technologies of computer security are based on logic. There is no universal standard notion of what secure behavior is. "Security" is a concept that is unique to each situation. Security is extraneous to the function of a computer application, rather than ancillary to it, thus security necessarily imposes restrictions on the application's behavior.

There are several approaches to security in computing, sometimes a combination of approaches is valid:

1. Trust all the software to abide by a security policy but the software is not trustworthy (this is computer insecurity).
2. Trust all the software to abide by a security policy and the software is validated as trustworthy (by tedious branch and path analysis for example).
3. Trust no software but enforce a security policy with mechanisms that are not trustworthy (again this is computer insecurity).
4. Trust no software but enforce a security policy with trustworthy mechanisms.

Many systems have unintentionally resulted in the first possibility. Since approach two is expensive and non-deterministic, its use is very limited. Approaches one and three lead to failure. Because approach number four is often based on hardware mechanisms and avoids abstractions and a multiplicity of degrees of freedom, it is more practical. Combinations of approaches two and four are often used in a layered architecture with thin layers of two and thick layers of four.

There are myriad strategies and techniques used to design security systems. There are few, if any, effective strategies to enhance security after design.

One technique enforces the principle of least privilege to great extent, where an entity has only the privileges that are needed for its function. That way even if an attacker gains access to one part of the system, fine-grained security ensures that it is just as difficult for them to access the rest.

Furthermore, by breaking the system up into smaller components, the complexity of individual components is reduced, opening up the possibility of using techniques such as automated theorem proving to prove the correctness of crucial software subsystems. This enables a closed form solution to security that works well when only a single well-characterized property can be isolated as critical, and that property is also assessable to math. Not surprisingly, it is impractical for generalized correctness, which probably cannot even be defined, much less proven. Where formal correctness proofs are not possible, rigorous use of code review and unit testing represent a best-effort approach to make modules secure.

The design should use "defense in depth", where more than one subsystem needs to be violated to compromise the integrity of the system and the information it holds. Defense in depth works when the breaching of one security measure does not provide a platform to facilitate subverting another. Also, the cascading principle acknowledges that several low hurdles does not make a high hurdle. So cascading several weak mechanisms does not provide the safety of a single stronger mechanism.

Subsystems should default to secure settings, and wherever possible should be designed to "fail secure" rather than "fail insecure" (see fail safe for the equivalent in safety engineering). Ideally, a secure system should require a deliberate, conscious, knowledgeable and free decision on the part of legitimate authorities in order to make it insecure.

In addition, security should not be an all or nothing issue. The designers and operators of systems should assume that security breaches are inevitable. Full audit trails should be kept of system activity, so that when a security breach occurs, the mechanism and extent of the breach can be determined. Storing audit trails remotely, where they can only be appended to, can keep intruders from covering their tracks. Finally, full disclosure helps to ensure that when bugs are found the "window of vulnerability" is kept as short as possible.

Early history of security by design

The early Multics operating system was notable for its early emphasis on computer security by design, and Multics was possibly the very first operating system to be designed as a secure system from the ground up. In spite of this, Multics' security was broken, not once, but repeatedly. The strategy was known as 'penetrate and test' and has become widely known as a non-terminating process that fails to produce computer security. This led to further work on computer security that prefigured modern security engineering techniques producing closed form processes that terminate.

Secure coding

If the operating environment is not based on a secure operating system capable of maintaining a domain for its own execution, and capable of protecting application code from malicious subversion, and capable of protecting the system from subverted code, then high degrees of security are understandably not possible. While such secure operating systems are possible and have been implemented, most commercial systems fall in a 'low security' category because they rely on features not supported by secure operating systems (like portability, et al.). In low security operating environments, applications must be relied on to participate in their own protection. There are 'best effort' secure coding practices that can be followed to make an application more resistant to malicious subversion.

In commercial environments, the majority of software subversion vulnerabilities result from a few known kinds of coding defects. Common software defects include buffer overflows, format string vulnerabilities, integer overflow, and code/command injection.

Some common languages such as C and C++ are vulnerable to all of these defects (see Seacord, "Secure Coding in C and C++"). Other languages, such as Java, are more resistant to some of these defects, but are still prone to code/command injection and other software defects which facilitate subversion.

Recently another bad coding practice has come under scrutiny; dangling pointers. The first known exploit for this particular problem was presented in July 2007. Before this publication the problem was known but considered to be academic and not practically exploitable.

In summary, 'secure coding' can provide significant payback in low security operating environments, and therefore worth the effort. Still there is no known way to provide a reliable degree of subversion resistance with any degree or combination of 'secure coding.'

Capabilities vs. ACLs

Within computer systems, the two fundamental means of enforcing privilege separation are access control lists (ACLs) and capabilities. The semantics of ACLs have been proven to be insecure in many situations (e.g., Confused deputy problem). It has also been shown that ACL's promise of giving access to an object to only one person can never be guaranteed in practice. Both of these problems are resolved by capabilities. This does not mean practical flaws exist in all ACL-based systems, but only that the designers of certain utilities must take responsibility to ensure that they do not introduce flaws.

Unfortunately, for various historical reasons, capabilities have been mostly restricted to research operating systems and commercial OSs still use ACLs. Capabilities can, however, also be implemented at the language level, leading to a style of programming that is essentially a refinement of standard object-oriented design. An open source project in the area is the E language.

First the Plessey System 250 and then Cambridge CAP computer demonstrated the use of capabilities, both in hardware and software, in the 1970s, so this technology is hardly new. A reason for the lack of adoption of capabilities may be that ACLs appeared to offer a 'quick fix' for security without pervasive redesign of the operating system and hardware.

The most secure computers are those not connected to the Internet and shielded from any interference. In the real world, the most security comes from operating systems where security is not an add-on, such as OS/400 from IBM. This almost never shows up in lists of vulnerabilities for good reason. Years may elapse between one problem needing remediation and the next.

A good example of a secure system is EROS. But see also the article on secure operating systems. TrustedBSD is an example of an open source project with a goal, among other things, of building capability functionality into the FreeBSD operating system. Much of the work is already done.

Applications

Computer security is critical in almost any technology-driven industry which operates on computer systems. The issues of computer based systems and addressing their countless vulnerabilities are an integral part of maintaining an operational industry.

In aviation

The aviation industry is especially important when analyzing computer security because the involved risks include expensive equipment and cargo, transportation infrastructure, and human life. Security can be compromised by hardware and software malpractice, human error, and faulty operating environments. Threats that exploit computer vulnerabilities can stem from sabotage, espionage, industrial competition, terrorist attack, mechanical malfunction, and human error.

The consequences of a successful deliberate or inadvertent misuse of a computer system in the aviation industry range from loss of confidentiality to loss of system integrity, which may lead to more serious concerns such as data theft or loss, network and air traffic control outages, which in turn can lead to airport closures, loss of aircraft, loss of passenger life. Military systems that control munitions can pose an even greater risk.

A proper attack does not need to be very high tech or well funded for a power outage at an airport alone can cause repercussions worldwide. One of the easiest and, arguably, the most difficult to trace security vulnerabilities is achievable by transmitting unauthorized communications over specific radio frequencies. These transmissions may spoof air traffic controllers or simply disrupt communications altogether. These incidents are very common, having altered flight courses of commercial aircraft and caused panic and confusion in the past. Controlling aircraft over oceans is especially dangerous because radar surveillance only extends 175 to 225 miles offshore. Beyond the radar's sight controllers must rely on periodic radio communications with a third party.

Lightning, power fluctuations, surges, brown-outs, blown fuses, and various other power outages instantly disable all computer systems, since they are dependent on electrical source. Other accidental and intentional faults have caused significant disruption of safety critical systems throughout the last few decades and dependence on reliable communication and electrical power only jeopardizes computer safety.

[edit] Notable system accidents

In 1994, over a hundred intrusions were made by unidentified hackers into the Rome Laboratory, the US Air Force's main command and research facility. Using trojan horse viruses, hackers were able to obtain unrestricted access to Rome's networking systems and remove traces of their activities. The intruders were able to obtain classified files, such as air tasking order systems data and furthermore able to penetrate connected networks of National Aeronautics and Space Administration's Goddard Space Flight Center, Wright-Patterson Air Force Base, some Defense contractors, and other private sector organizations, by posing as a trusted Rome center user. Now, a technique called Ethical hack testing is used to remediate these issues.

Electromagnetic interference is another threat to computer safety and in 1989, a United States Air Force F-16 jet accidentally dropped a 230 kg bomb in West Georgia after unspecified interference caused the jet's computers to release it.

A similar telecommunications accident also happened in 1994, when two UH-60 Blackhawk helicopters were destroyed by F-15 aircraft in Iraq because the IFF system's encryption system malfunctioned.^{[citation needed]}

Terminology

The following terms used in engineering secure systems are explained below.

• A bigger OS, capable of providing a standard API like POSIX, can be built on a secure microkernel using small API servers running as normal programs. If one of these API servers has a bug, the kernel and the other servers are not affected: e.g. Hurd or Minix 3.
• authentication techniques can be used to ensure that communication end-points are who they say they are.
• Automated theorem proving and other verification tools can enable critical algorithms and code used in secure systems to be mathematically proven to meet their specifications.
• Capability and access control list techniques can be used to ensure privilege separation and mandatory access control. The next sections discuss their use.
• Chain of trust techniques can be used to attempt to ensure that all software loaded has been certified as authentic by the system's designers.
• Cryptographic techniques can be used to defend data in transit between systems, reducing the probability that data exchanged between systems can be intercepted or modified.
• Firewalls can either be hardware devices or software programs. They provide some protection from online intrusion, but since they allow some applications (e.g. web browsers) to connect to the Internet, they don't protect against some unpatched vulnerabilities in these applications (e.g. lists of known unpatched holes from Secunia and SecurityFocus).
• Mandatory access control can be used to ensure that privileged access is withdrawn when privileges are revoked. For example, deleting a user account should also stop any processes that are running with that user's privileges.
• Secure cryptoprocessors can be used to leverage physical security techniques into protecting the security of the computer system.
• Thus simple microkernels can be written so that we can be sure they don't contain any bugs: eg EROS and Coyotos.

Some of the following items may belong to the computer insecurity article:

• Access authorization restricts access to a computer to group of users through the use of authentication systems. These systems can protect either the whole computer - such as through an interactive logon screen - or individual services, such as an FTP server. There are many methods for identifying and authenticating users, such as passwords, identification cards, and, more recently, smart cards and biometric systems.
• Anti-virus software consists of computer programs that attempt to identify, thwart and eliminate computer viruses and other malicious software (malware).
• application with known security flaws should not be run. Either leave it turned off until it can be patched or otherwise fixed, or delete it and replace it with some other application. Publicly known flaws are the main entry used by worms to automatically break into a system and then spread to other systems connected to it. The security website Secunia provides a search tool for unpatched known flaws in popular products.

Cryptographic techniques involve transforming information, scrambling it so it becomes unreadable during transmission. The intended recipient can unscramble the message, but eavesdroppers cannot.

• Backups are a way of securing information; they are another copy of all the important computer files kept in another location. These files are kept on hard disks, CD-Rs, CD-RWs, and tapes. Suggested locations for backups are a fireproof, waterproof, and heat proof safe, or in a separate, offsite location than that in which the original files are contained. Some individuals and companies also keep their backups in safe deposit boxes inside bank vaults. There is also a fourth option, which involves using one of the file hosting services that backs up files over the Internet for both business and individuals.
  • Backups are also important for reasons other than security. Natural disasters, such as earthquakes, hurricanes, or tornadoes, may strike the building where the computer is located. The building can be on fire, or an explosion may occur. There needs to be a recent backup at an alternate secure location, in case of such kind of disaster. Further, it is recommended that the alternate location be placed where the same disaster would not affect both locations. Examples of alternate disaster recovery sites being compromised by the same disaster that affected the primary site include having had a primary site in World Trade Center I and the recovery site in 7 World Trade Center, both of which were destroyed in the 9/11 attack, and having one's primary site and recovery site in the same coastal region, which leads to both being vulnerable to hurricane damage (e.g. primary site in New Orleans and recovery site in Jefferson Parish, both of which were hit by Hurricane Katrina in 2005). The backup media should be moved between the geographic sites in a secure manner, in order to prevent them from being stolen.
• Encryption is used to protect the message from the eyes of others. It can be done in several ways by switching the characters around, replacing characters with others, and even removing characters from the message. These have to be used in combination to make the encryption secure enough, that is to say, sufficiently difficult to crack. Public key encryption is a refined and practical way of doing encryption. It allows for example anyone to write a message for a list of recipients, and only those recipients will be able to read that message.
• Firewalls are systems which help protect computers and computer networks from attack and subsequent intrusion by restricting the network traffic which can pass through them, based on a set of system administrator defined rules.
• Honey pots are computers that are either intentionally or unintentionally left vulnerable to attack by crackers. They can be used to catch crackers or fix vulnerabilities.
• Intrusion-detection systems can scan a network for people that are on the network but who should not be there or are doing things that they should not be doing, for example trying a lot of passwords to gain access to the network.
• Pinging The ping application can be used by potential crackers to find if an IP address is reachable. If a cracker finds a computer they can try a port scan to detect and attack services on that computer.
• Social engineering awareness keeps employees aware of the dangers of social engineering and/or having a policy in place to prevent social engineering can reduce successful breaches of the network and servers.

Linux

.

Linux

OS family	Unix-like
Working state	Current
Latest stable release	2.6.28.4 (February 6, 2009)
Latest unstable release	2.6.29-rc3-git3 (Feb 01, 2009)
Kernel type	Monolithic kernel
License	Components released under GNU General Public License and others

Linux is a generic term referring to Unix-like computer operating systems based on the Linux kernel. Their development is one of the most prominent examples of free and open source software collaboration; typically all the underlying source code can be used, freely modified, and redistributed by anyone under the terms free licenses.

Linux distributions are predominantly known for their use in servers, although they are installed on a wide variety of computer hardware, ranging from embedded devices and mobile phones to supercomputers,^[3] and their popularity as a desktop/laptop operating system has been growing lately due to the rise of netbooks and the Ubuntu distribution of the operating system.^[4][5]

The name "Linux" comes from the Linux kernel, originally written in 1991 by Linus Torvalds. The rest of the system, including utilities and libraries, usually comes from the GNU operating system announced in 1983 by Richard Stallman. The GNU contribution is the basis for the alternative name GNU/Linux.

History

Richard Stallman, left, founder of the GNU project, and Linus Torvalds, right, creator of the Linux kernel

The Unix operating system was conceived and implemented in the 1960s and first released in 1970. Its wide availability and portability meant that it was widely adopted, copied and modified by academic institutions and businesses, with its design being influential on authors of other systems.

The GNU Project, started in 1984 by Richard Stallman, had the goal of creating a "complete Unix-compatible software system made entirely of free software. The next year Stallman created the Free Software Foundation and wrote the GNU General Public License (GNU GPL) in 1989. By the early 1990s, many of the programs required in an operating system (such as libraries, compilers, text editors, a Unix shell, and a windowing system) were completed, although low-level elements such as device drivers, daemons, and the kernel were stalled and incomplete.^[8] Linus Torvalds has said that if the GNU kernel had been available at the time (1991), he would not have decided to write his own.^[9]

[edit] MINIX

Further information: Tanenbaum-Torvalds debate

MINIX, a Unix-like system intended for academic use, was released by Andrew S. Tanenbaum in 1987. While source code for the system was available, modification and redistribution were restricted (that is not the case today). In addition, MINIX's 16-bit design was not well adapted to the 32-bit design of the increasingly cheap and popular Intel 386 architecture for personal computers.

In 1991 while attending the University of Helsinki, Torvalds began to work on a non-commercial replacement for MINIX , which would eventually become the Linux kernel. In 1992, Tanenbaum posted an article on Usenet claiming Linux was obsolete. In the article, he criticized the operating system as being monolithic in design and being tied closely to the x86 architecture and thus not portable, as he described "a fundamental error."^[11] Tanenbaum suggested that those who wanted a modern operating system should look into one based on the microkernel model. The posting elicited the response of Torvalds, which resulted in a well known debate over the microkernel and monolithic kernel designs.^[11]

Linux was dependent on the MINIX user space at first. With code from the GNU system freely available, it was advantageous if this could be used with the fledgling OS. Code licensed under the GNU GPL can be used in other projects, so long as they also are released under the same or a compatible license. In order to make the Linux kernel compatible with the components from the GNU Project, Torvalds initiated a switch from his original license (which prohibited commercial redistribution) to the GNU GPL. Developers worked to integrate GNU components with Linux to make a fully functional and free operating system.

Commercial and popular uptake

Today Linux distributions are used in numerous domains, from embedded systems to supercomputers, and have secured a place in server installations with the popular LAMP application stack. Use of Linux distributions in home and enterprise desktops has been rapidly expanding and now claims a significant share of the desktop market.

Linux distributions have also become popular with the newly founded netbook market, with many devices such as the ASUS Eee PC and Acer Aspire One shipping with customized Linux distributions pre-installed.

Current development

Torvalds continues to direct the development of the kernel. Stallman heads the Free Software Foundation, which in turn supports the GNU components. Finally, individuals and corporations develop third-party non-GNU components. These third-party components comprise a vast body of work and may include both kernel modules and user applications and libraries. Linux vendors and communities combine and distribute the kernel, GNU components, and non-GNU components, with additional package management software in the form of Linux distributions.

Design

Main components of Linux operating system

A Linux-based system is a modular Unix-like operating system. It derives much of its basic design from principles established in Unix during the 1970s and 1980s. Such a system uses a monolithic kernel, the Linux kernel, which handles process control, networking, and peripheral and file system access. Device drivers are integrated directly with the kernel.

Separate projects that interface with the kernel provide much of the system's higher-level functionality. The GNU userland is an important part of most Linux-based systems, providing the most common implementation of the C library, a popular shell, and many of the common Unix tools which carry out many basic operating system tasks. The graphical user interface on most Linux systems is based on the X Window System.

User interfa

A Linux-based system can be controlled by one or more of a text-based command line interface (CLI), graphical user interface (GUI) (usually the default for desktop), or through controls on the device itself (common on embedded machines).

On desktop machines, KDE, GNOME and Xfce are the most popular user interfaces,^[23] though a variety of other user interfaces exist. Most popular user interfaces run on top of the X Window System (X), which provides network transparency, enabling a graphical application running on one machine to be displayed and controlled from another.

Other GUIs include X window managers such as FVWM, Enlightenment and Window Maker. The window manager provides a means to control the placement and appearance of individual application windows, and interacts with the X window system.

A Linux system typically provides a CLI of some sort through a shell, which is the traditional way of interacting with a Unix system. A Linux distribution specialized for servers may use the CLI as its only interface. A “headless system” run without even a monitor can be controlled by the command line via a remote-control protocol such as SSH or telnet.

Most low-level Linux components, including the GNU Userland, use the CLI exclusively. The CLI is particularly suited for automation of repetitive or delayed tasks, and provides very simple inter-process communication. A graphical terminal emulator program is often used to access the CLI from a Linux desktop.

Development

A summarised history of Unix-like operating systems showing Linux's origins. Note that despite similar architectural designs and concepts being shared as part of the POSIX standard, Linux does not share any non-free source code with the original Unix or Minix.

The primary difference between Linux and many other popular contemporary operating systems is that the Linux kernel and other components are free and open source software. Linux is not the only such operating system, although it is the best-known and most widely used. Some free and open source software licences are based on the principle of copyleft, a kind of reciprocity: any work derived from a copyleft piece of software must also be copyleft itself. The most common free software license, the GNU GPL, is a form of copyleft, and is used for the Linux kernel and many of the components from the GNU project.

As an operating system underdog competing with mainstream operating systems, Linux based distributions cannot rely on a monopoly advantage; in order for distributions to be convenient for users, developers aim for interoperability with other operating systems and established computing standards. Linux systems adhere to POSIX,SUS, ISO and ANSI standards where possible, although to date only one Linux distribution has been POSIX.1 certified, Linux-FT.

Free software projects, although developed in a collaborative fashion, are often produced independently of each other. The fact that the software licenses explicitly permit redistribution, however, provides a basis for larger scale projects that collect the software produced by stand-alone projects and make it available all at once in the form of a Linux distribution.

A Linux distribution, commonly called a “distro”, is a project that manages a remote collection of system software and application software packages available for download and installation through a network connection. This allows the user to adapt the operating system to his/her specific needs. Distributions are maintained by individuals, loose-knit teams, volunteer organizations, and commercial entities. A distribution can be installed using a CD that contains distribution-specific software for initial system installation and configuration. A package manager such as Synaptic allows later package upgrades and installs. A distribution is responsible for the default configuration of the installed Linux kernel, general system security, and more generally integration of the different software packages into a coherent whole.

Community

See also: Free software community

A distribution is largely driven by its developer and user communities. Some vendors develop and fund their distributions on a volunteer basis, Debian being a well-known example. Others maintain a community version of their commercial distributions, as Red Hat does with Fedora.

In many cities and regions, local associations known as Linux Users Groups (LUGs) seek to promote their preferred distribution and by extension free software. They hold meetings and provide free demonstrations, training, technical support, and operating system installation to new users. Many Internet communities also provide support to Linux users and developers. Most distributions and free software / open source projects have IRC chatrooms or newsgroups. Online forums are another means for support, with notable examples being LinuxQuestions.org and the Gentoo forums. Linux distributions host mailing lists; commonly there will be a specific topic such as usage or development for a given list.

There are several technology websites with a Linux focus. Print magazines on Linux often include cover disks including software or even complete Linux distributions.

Although Linux distributions are generally available without charge, several large corporations sell, support, and contribute to the development of the components of the system and of free software. These include Dell, IBM, HP, Oracle, Sun Microsystems, Novell, Nokia. A number of corporations, notably Red Hat, have built their entire business around Linux distributions.

The free software licenses, on which the various software packages of a distribution built on the Linux kernel are based, explicitly accommodate and encourage commercialization; the relationship between a Linux distribution as a whole and individual vendors may be seen as symbiotic. One common business model of commercial suppliers is charging for support, especially for business users. A number of companies also offer a specialized business version of their distribution, which adds proprietary support packages and tools to administer higher numbers of installations or to simplify administrative tasks. Another business model is to give away the software in order to sell hardware.

Programming on Linux

Most Linux distributions support dozens of programming languages. The most common collection of utilities for building both Linux applications and operating system programs is found within the GNU toolchain, which includes the GNU Compiler Collection (GCC) and the GNU build system. Amongst others, GCC provides compilers for Ada, C, C++, Java, and Fortran. The Linux kernel itself is written to be compiled with GCC. Proprietary compilers for Linux include the Intel C++ Compiler and IBM XL C/C++ Compiler.

Most distributions also include support for Perl, Ruby, Python and other dynamic languages. Examples of languages that are less common, but still well-supported, are C# via the Mono project, sponsored by Novell, and Scheme. A number of Java Virtual Machines and development kits run on Linux, including the original Sun Microsystems JVM (HotSpot), and IBM's J2SE RE, as well as many open-source projects like Kaffe.

The two main frameworks for developing graphical applications are those of GNOME and KDE. These projects are based on the GTK+ and Qt widget toolkits, respectively, which can also be used independently of the larger framework. Both support a wide variety of languages. There are a number of Integrated development environments available including Anjuta, Code::Blocks, Eclipse, KDevelop, Lazarus, MonoDevelop, NetBeans, and Omnis Studio while the long-established editors Vim and Emacs remain popular.

Uses

The Linux kernel can run on Windows
As well as those designed for general purpose use on desktops and servers, distributions may be specialized for different purposes including: computer architecture support, embedded systems, stability, security, localization to a specific region or language, targeting of specific user groups, support for real-time applications, or commitment to a given desktop environment. Furthermore, some distributions deliberately include only free software. Currently, over three hundred distributions are actively developed, with about a dozen distributions being most popular for general-purpose use.

Linux is a widely ported operating system kernel. The Linux kernel runs on the most diverse range of computer architectures: in the hand-held ARM-based iPAQ and the mainframe IBM System z9, in devices ranging from mobile phones to supercomputers.Specialized distributions exist for less mainstream architectures. The ELKS kernel fork can run on Intel 8086 or Intel 80286 16-bit microprocessors, while the µClinux kernel fork may run on systems without a memory management unit. The kernel also runs on architectures that were only ever intended to use a manufacturer-created operating system, such as Macintosh computers (with both PowerPC and Intel processors), PDAs, video game consoles, portable music players, and mobile phone

Intel Corporation

Intel Corporation is the world's largest company and the inventor of the x86 series of microprocessors, the processors found in most p.c . Founded on July 18, 1968 as Integrated Electronics Corporation and based in USA , Intel also makes graphic chips, embedded processors, and other devices related to communications and computing. Founded by semiconductor pioneers and widely associated with the executive leadership and vision . Intel combines advanced chip design capability with a leading-edge manufacturing capability. Originally known primarily to engineers and technologists, Intel's successful "Intel Inside" advertising campaign of the 1990s made it and its household names.

Intel was an early developer of SRAM $ DRAM memory chips, and this represented the majority of its business until the early 1980s. While Intel created the first commercial microprocessor chip in 1971, it was not until the success of the (PC) that this became their primary business. During the 1990s, Intel invested heavily in new microprocessor designs fostering the rapid growth of the PC industry. During this period Intel became the supplier of microprocessors for PCs, and was known for aggressive and sometimes controversial tactics in defense of its market position, as well as a struggle with MICROSOFT control over the direction of the PC industry. The 2007 rankings of the world's 100 most powerful brands published showed the company's brand value falling 10 places – from number 15 to number 25.

Market history

SRAMS and the microprocessor

The company's first products were shift register memory and random-access memory integrated circuits, and Intel grew to be a leader in the fiercely competitive DRAM, SRAM, and ROM markets throughout the 1970s. Concurrently, Intel engineers Marcian Hoff, Federico Faggin, Stanley Mazor and Masatoshi Shima invented the first microprocessor. Originally developed for the Japanese company Busicom to replace a number of ASICs in a calculator already produced by Busicom, the Intel 4004 was introduced to the mass market on November 15, 1971, though the microprocessor did not become the core of Intel's business until the mid-1980s. (Note: Intel is usually given credit with Texas Instruments for the almost-simultaneous invention of the microprocessor.)

[edit] From DRAM to microprocessors

In 1983, at the dawn of the personal computer era, Intel's profits came under increased pressure from Japanese memory-chip manufacturers, and then-President Andy Grove drove the company into a focus on microprocessors. Grove described this transition in the book Only the Paranoid Survive. A key element of his plan was the notion, then considered radical, of becoming the single source for successors to the popular 8086 microprocessor.

Until then, manufacture of complex integrated circuits was not reliable enough for customers to depend on a single supplier, but Grove began producing processors in three geographically distinct factories, and ceased licensing the chip designs to competitors such as Zilog and AMD. When the PC industry boomed in the late 1980s and 1990s, Intel was one of the primary beneficiaries.

[edit] Intel, x86 processors, and the IBM PC

The integrated circuit from an Intel 8742, an 8-bit microcontroller that includes a CPU running at 12 MHz, 128 bytes of RAM, 2048 bytes of EPROM, and I/O in the same chip.

Despite the ultimate importance of the microprocessor, the 4004 and its successors the 8008 and the 8080 were never major revenue contributors at Intel. As the next processor, the 8086 (and its variant the 8088) was completed in 1978, Intel embarked on a major marketing and sales campaign for that chip nicknamed "Operation Crush", and intended to win as many customers for the processor as possible. One design win was the newly-created IBM PC division, though the importance of this was not fully realized at the time.

IBM introduced its personal computer in 1981, and it was rapidly successful. In 1982, Intel created the 80286 microprocessor, which, two years later, was used in the IBM PC/AT. Compaq, the first IBM PC "clone" manufacturer, produced a desktop system based on the faster 80286 processor in 1985 and in 1986 quickly followed with the first 80386-based system, beating IBM and establishing a competitive market for PC-compatible systems and setting up Intel as a key component supplier.

In 1975 the company had started a project to develop a highly-advanced 32-bit microprocessor, finally released in 1981 as the Intel iAPX 432. The project was too ambitious and the processor was never able to meet its performance objectives, and it failed in the marketplace. Intel extended the x86 architecture to 32 bits instead.^[16][17]

[edit] 386 microprocessor

During this period Andrew Grove dramatically redirected the company, closing much of its DRAM business and directing resources to the microprocessor business. Of perhaps greater importance was his decision to "single-source" the 386 microprocessor. Prior to this, microprocessor manufacturing was in its infancy, and manufacturing problems frequently reduced or stopped production, interrupting supplies to customers. To mitigate this risk, these customers typically insisted that multiple manufacturers produce chips they could use to ensure a consistent supply. The 8080 and 8086-series microprocessors were produced by several companies, notably Zilog and AMD. Grove made the decision not to license the 386 design to other manufacturers, instead producing it in three geographically distinct factories in Santa Clara, California; Hillsboro, Oregon; and the Phoenix, Arizona suburb of Chandler; and convincing customers that this would ensure consistent delivery. As the success of Compaq's Deskpro 386 established the 386 as the dominant CPU choice, Intel achieved a position of near-exclusive dominance as its supplier. Profits from this funded rapid development of both higher-performance chip designs and higher-performance manufacturing capabilities, propelling Intel to a position of unquestioned leadership by the early 1990s.

[edit] 486, Pentium, and Itanium

Intel introduced the 486 microprocessor in 1989, and in 1990 formally established a second design team, designing the processors code-named "P5" and "P6" in parallel and committing to a major new processor every two years, versus the four or more years such designs had previously taken. The P5 was earlier known as "Operation Bicycle" referring to the cycles of the processor. The P5 was introduced in 1993 as the Intel Pentium, substituting a trademarked name for the former part number (numbers, like 486, cannot be trademarked). The P6 followed in 1995 as the Pentium Pro and improved into the Pentium II in 1997. New architectures were developed alternately in Santa Clara, California and Hillsboro, Oregon.

The Santa Clara design team embarked in 1993 on a successor to the x86 architecture, codenamed "P7". The first attempt was dropped a year later, but quickly revived in a cooperative program with Hewlett-Packard engineers, though Intel soon took over primary design responsibility. The resulting implementation of the IA-64 64-bit architecture was the Itanium, finally introduced in June 2001. The Itanium's performance running legacy x86 code did not achieve expectations, and it failed to effectively compete with 64-bit extensions to the original x86 architecture, first from AMD (the AMD64), then from Intel itself (the Intel 64 architecture, formerly known as EM64T). As of November 2007, Intel continues to develop and deploy the Itanium.

The Hillsboro team designed the Willamette processor (code-named P67 and P68) which was marketed as the Pentium 4, and later developed the 64-bit extensions to the x86 architecture, present in some versions of the Pentium 4 and in the Intel Core 2 chips. Many chip variants were developed at an office in Haifa, Israel.

[edit] Pentium flaw

Main article: Pentium FDIV bug

In June 1994, Intel engineers discovered a flaw in the floating-point math subsection of the Pentium microprocessor. Under certain data dependent conditions, low order bits of the result of floating-point division operations would be incorrect, an error that can quickly compound in floating-point operations to much larger errors in subsequent calculations. Intel corrected the error in a future chip revision, but nonetheless declined to disclose it.^{[citation needed]}

In October 1994, Dr. Thomas Nicely, Professor of Mathematics at Lynchburg College independently discovered the bug, and upon receiving no response from his inquiry to Intel, on October 30 posted a message on the Internet.^[18] Word of the bug spread quickly on the Internet and then to the industry press. Because the bug was easy to replicate by an average user (there was a sequence of numbers one could enter into the OS calculator to show the error), Intel's statements that it was minor and "not even an erratum" were not accepted by many computer users. During Thanksgiving 1994, The New York Times ran a piece by journalist John Markoff spotlighting the error. Intel changed its position and offered to replace every chip, quickly putting in place a large end-user support organization. This resulted in a $500 million charge against Intel's 1994 revenue.

Ironically, the "Pentium flaw" incident, Intel's response to it, and the surrounding media coverage propelled Intel from being a technology supplier generally unknown to most computer users to a household name. Dovetailing with an uptick in the "Intel Inside" campaign, the episode is considered by some to have been a positive event for Intel, changing some of its business practices to be more end-user focused and generating substantial public awareness, while avoiding (for most users) a lasting negative impression.^[19]

[edit] Intel Inside, Intel Systems Division, and Intel Architecture Labs

During this period, Intel undertook two major supporting programs that helped guarantee their processor's success. The first is widely-known: the 1990 "Intel Inside" marketing and branding campaign. This campaign established Intel, which had been a component supplier little-known outside the PC industry, as a household name. The second program is little-known: Intel's Systems Group began, in the early 1990s, manufacturing PC "motherboards", the main board component of a personal computer, and the one into which the processor (CPU) and memory (RAM) chips are plugged. Shortly after, Intel began manufacturing fully-configured "white box" systems for the dozens of PC clone companies that rapidly sprang up. At its peak in the mid-1990s, Intel manufactured over 15% of all PCs, making it the third-largest supplier at the time. By manufacturing leading-edge PC motherboards systems, Intel enabled smaller manufacturers to compete with larger manufacturers, accelerating the adoption of the newest microprocessors and system architecture, including the PCI bus, USB and other innovations. This led to more rapid adoption of each of its new processors in turn.^{[citation needed]}

During the 1990s, Intel's Architecture Lab (IAL) was responsible for many of the hardware innovations of the personal computer, including the PCI Bus, the PCI Express (PCIe) bus, the Universal Serial Bus (USB), Bluetooth wireless interconnect, and the now-dominant architecture for multiprocessor servers. IAL's software efforts met with a more mixed fate; its video and graphics software was important in the development of software digital video, but later its efforts were largely overshadowed by competition from Microsoft. The competition between Intel and Microsoft was revealed in testimony by IAL Vice-President Steven McGeady at the Microsoft antitrust trial.

Another factor contributing to rapid adoption of Intel's processors during this period were the successive release of Microsoft Windows operating systems, each requiring significantly greater processor resources. The releases of Windows 95, Windows 98, and Windows 2000 provided impetus for successive generations of hardware.

[edit] Competition, antitrust and espionage

See also: AMD v. Intel

Two factors combined to end this dominance: the slowing of PC demand growth beginning in 2000 and the rise of the low cost PC. By the end of the 1990s, microprocessor performance had outstripped software demand for that CPU power. Aside from high-end server systems and software, demand for which dropped with the end of the "dot-com bubble", consumer systems ran effectively on increasingly low-cost systems after 2000. Intel's strategy of producing ever-more-powerful processors and obsoleting their predecessors stumbled, leaving an opportunity for rapid gains by competitors, notably AMD. This in turn lowered the profitability of the processor line and ended an era of unprecedented dominance of the PC hardware by Intel.^{[citation needed]}

Intel's dominance in the x86 microprocessor market led to numerous charges of antitrust violations over the years, including FTC investigations in both the late 1980s and in 1999, and civil actions such as the 1997 suit by Digital Equipment Corporation (DEC) and a patent suit by Intergraph. Intel's market dominance (at one time it controlled over 85% of the market for 32-bit PC microprocessors) combined with Intel's own hardball legal tactics (such as its infamous 338 patent suit versus PC manufacturers)^[20] made it an attractive target for litigation, but few of the lawsuits ever amounted to anything.

A case of industrial espionage arose in 1995 that involved both Intel and AMD. Guillermo Gaede, an Argentine formerly employed both at AMD and at Intel's Arizona plant, was arrested for attempting in 1993 to sell the i486 and Pentium designs to AMD and to certain foreign powers.^[21] Gaede videotaped data from his computer screen at Intel and mailed it to AMD, which immediately alerted Intel and authorities, resulting in Gaede's arrest. Gaede was convicted and sentenced to 33 months in prison in June 1996.^[22][23]

[edit] Partnership with Apple

For more details on this topic, see Apple Intel transition.

On June 6, 2005, Apple CEO Steve Jobs announced that Apple would be transitioning from its long favored PowerPC architecture to the Intel x86 architecture, because the future PowerPC road map was unable to satisfy Apple's needs. The first Macintosh computers containing Intel CPUs were announced on January 10, 2006, and Apple had its entire line of consumer Macs running on Intel processors by early August 2006. The Apple Xserve server was updated to Intel Xeon processors from November 2006, and is offered in a configuration similar to Apple's Mac Pro.^[24]

[edit] Core 2 Duo advertisement controversy

In 2007, the company released a print advertisement for its Core 2 Duo processor featuring six African American runners appearing to bow down to a Caucasian male inside of an office setting (due to the posture taken by runners on starting blocks). According to Nancy Bhagat, Vice President of Intel Corporate Marketing, the general public found the ad to be "insensitive and insulting".^[25] The campaign was quickly pulled and several Intel executives made public apologies on the corporate website.^[26]

[edit] Corporate affairs

In September 2006, Intel had nearly 100,000 employees and 200 facilities world wide. Its 2005 revenues were $38.8 billion and its Fortune 500 ranking was 49th. Its stock symbol is INTC, listed on the NASDAQ.

[edit] Leadership and corporate structure

Robert Noyce was Intel's CEO at its founding in 1968, followed by co-founder Gordon Moore in 1975. Andy Grove became the company's President in 1979 and added the CEO title in 1987 when Moore became Chairman. In 1997 Grove succeeded Moore as Chairman, and Craig Barrett, already company president, took over. On May 18, 2005, Barrett handed the reins of the company over to Paul Otellini, who previously was the company president and was responsible for Intel's design win in the original IBM PC. The board of directors elected Otellini CEO, and Barrett replaced Grove as Chairman of the Board. Grove stepped down as Chairman, but is retained as a special adviser.

Current members of the board of directors of Intel are Craig Barrett, Charlene Barshefsky, Susan Decker, James Guzy, Reed Hundt, Paul Otellini, James Plummer, David Pottruck, Jane Shaw, John Thornton, and David Yoffie.^[27]