Computer Viruses

Small, executable software programs that replicate themselves using another program as a host. Just as biological viruses pass from person to person through contact, computer viruses pass from computer to computer. These viruses typically do damage (delete files) or cause infected computers to function inappropriately (send out messages automatically). In addition to their method of infection, computer viruses share other characteristics of their biological namesake, specifically ubiquity, difficulty of avoidance, and expense in terms of damage and lost productivity.

Computer viruses are distinguished from other damaging code (called malware), such as Trojan horses and computer worms. Trojan horses are computer programs that claim to do one thing but in fact do something altogether different. In a Trojan horse attack, an unsuspecting person might download software that claims do something benign, only to fall prey to a malicious attack, such as having his or her hard drive erased. Typically, a Trojan horse might silently allow others back-door access to the infected machines, at which point passwords and other sensitive data can be collected without the user's knowledge.

Computer viruses spread through contact with infected files, whereas computer worms, which also cause significant damage, are unique in that they replicate on their own through networks by scanning for security holes. The first computer worm, the Internet Worm, made its appearance in 1988. Written by a Cornell PhD student, the worm contained a bug that caused infected machines to automatically create more copies of itself, eventually bringing many of the Internet's computers to a halt. Computer viruses became a part of the popular culture during the 1970s through science fiction, although they first proliferated at the advent of personal computing during the 1980s and had become fixtures in the modern consciousness by the late 1980s.

Although computer viruses were first spread through personal disk sharing, the bulk of today's viruses are delivered through the Internet as attachments. Viruses that infect applications through file transfer have been superceded by macro viruses and others that use computer scripting languages, primarily those of Microsoft. The Melissa and Love Bug viruses are two examples of macro viruses, both of which were estimated to have done tens of billions of dollars worth of damage. In the Microsoft Windows operating system, attachments or executable programs received through the Internet with extensions such as .exe, .vbs, .com, and .bat, among others, could be viruses and should be treated with caution.

Antivirus software is a critical part of computer security. However, the best defense is ensuring that the person or file server sharing an application is trustworthy. The U.S. government has several entities that deal with computer security. One of those entities, US-CERT, is a partnership between the U.S. Department of Homeland Security and the public and private sectors. Established in 2003 to protect the nation's Internet infrastructure, US-CERT is the operational arm of the National Cyber Security Division at the Department of Homeland Security. As such, it coordinates defense against and responses to cyberattacks.

The Computer Security Division of the National Institute of Standards and Technology (NIST) is charged with improving information systems security for consumers and federal government systems. With the signing of the National Security Decision Directive in 1984, the National Security Agency (NSA) was made responsible for computer security throughout the United States. The 1987 Computer Security Act gave NIST responsibility for the security of nonclassified, nonmilitary government systems, but since then a power struggle has ensued between the NSA and NIST. In addition to government agencies, Carnegie Mellon University's Computer Emergency Response Team is a federally funded frontline defense and research organization dedicated to discovering and containing security vulnerabilities.

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