A computer virus is a computer program Computer programs are instructions for a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute the instructions. The same program in its human-readable source code form, from which executable that can copy itself[1] and infect a computer. The term "virus" is also commonly but erroneously used to refer to other types of malware Malware, short for malicious software, is software designed to infiltrate a computer system without the owner's informed consent. The expression is a general term used by computer professionals to mean a variety of forms of hostile, intrusive, or annoying software or program code. The term "computer virus" is sometimes used as a catch-, adware Adware or advertising-supported software is any software package which automatically plays, displays, or downloads advertisements to a computer after the software is installed on it or while the application is being used. Some types of adware are also spyware[citation needed] and can be classified as privacy-invasive software, and spyware Spyware is a type of malware that is installed on computers and collects information about users without their knowledge. The presence of spyware is typically hidden from the user. Typically, spyware is secretly installed on the user's personal computer. Sometimes, however, spywares such as keyloggers are installed by the owner of a shared, programs that do not have the reproductive ability. A true virus can only spread from one computer to another (in some form of executable code In communications, a code is a rule for converting a piece of information into another form or representation (one sign into another sign), not necessarily of the same type. In communications and information processing, encoding is the process by which information from a source is converted into symbols to be communicated. Decoding is the reverse) when its host is taken to the target computer; for instance because a user sent it over a network or the Internet, or carried it on a removable medium such as a floppy disk A floppy disk is a data storage medium that is composed of a disk of thin, flexible magnetic storage medium encased in a square or rectangular plastic shell, CD A Compact Disc is an optical disc used to store digital data. It was originally developed to store sound recordings exclusively, but later it also allowed the preservation of other types of data. Audio CDs have been commercially available since October 1982. In 2010, they remain the standard physical storage medium for audio, DVD DVD, also known as Digital Versatile Disc or Digital Video Disc, is an optical disc storage media format, and was developed and invented by Sony, and Philips in 1995. Its main uses are video and data storage. DVDs are of the same dimensions as compact discs , but store more than six times as much data, or USB drive A USB flash drive consists of flash memory data storage device integrated with a USB 1.1 or 2.0 interface. USB flash drives are typically removable and rewritable, much smaller than a floppy disk, and most weigh less than 30 g (1 oz). Storage capacities in 2009 can be as large as 256 GB with steady improvements in size and price per capacity. Some. Viruses can increase their chances of spreading to other computers by infecting files on a network file system A network file system is any computer file system that supports sharing of files, printers and other resources as persistent storage over a computer network. The first file servers were developed in the 1970s. In 1976 Digital Equipment Corporation created the File Access Listener an implementation of the Data Access Protocol as part of DECnet or a file system that is accessed by another computer.[2][3]
The term "computer virus" is sometimes used as a catch-all phrase to include all types of malware Malware, short for malicious software, is software designed to infiltrate a computer system without the owner's informed consent. The expression is a general term used by computer professionals to mean a variety of forms of hostile, intrusive, or annoying software or program code. The term "computer virus" is sometimes used as a catch-, adware Adware or advertising-supported software is any software package which automatically plays, displays, or downloads advertisements to a computer after the software is installed on it or while the application is being used. Some types of adware are also spyware[citation needed] and can be classified as privacy-invasive software, and spyware Spyware is a type of malware that is installed on computers and collects information about users without their knowledge. The presence of spyware is typically hidden from the user. Typically, spyware is secretly installed on the user's personal computer. Sometimes, however, spywares such as keyloggers are installed by the owner of a shared, programs that do not have the reproductive ability. Malware includes computer viruses, worms A computer worm is a self-replicating computer program. It uses a network to send copies of itself to other nodes and it may do so without any user intervention. Unlike a virus, it does not need to attach itself to an existing program. Worms almost always cause at least some harm to the network, if only by consuming bandwidth, whereas viruses, trojans, most rootkits, spyware, dishonest adware, crimeware, and other malicious and unwanted software, including true viruses. Viruses are sometimes confused with computer worms and Trojan horses A Trojan horse , is non-self-replicating malware that appears to perform a desirable function for the user but instead facilitates unauthorized access to the user's computer system. The term is derived from the Trojan Horse story in Greek mythology, which are technically different. A worm can exploit security vulnerabilities to spread itself to other computers without needing to be transferred as part of a host, and a Trojan horse is a program that appears harmless but has a hidden agenda. Worms and Trojans, like viruses, may cause harm to either a computer system's hosted data, functional performance, or networking throughput, when they are executed. Some viruses and other malware have symptoms noticeable to the computer user, but many are surreptitious or go unnoticed.
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