Computers today. Гурьянова В.И. - 30 стр.

able medium such as a floppy disk, CD, or USB drive. Additionally, viruses can
spread to other computers by infecting files on a network file system or a file system
that is accessed by another computer. Viruses are sometimes confused with computer
worms and Trojan horses. A worm, however, can spread itself to other computers be-
ing transferred as part of a host. A Trojan horse is a file that is harmless until executed.
In contrast to viruses, Trojan horses do not insert their code into other computer files.
Many personal computers are now connected to the Internet and to local-area net-
works, facilitating their spread. Today’s viruses may also take advantage of network
services such as the World Wide Web, e-mail, and file sharing systems to spread, blur-
ring the line between viruses and worms. Furthermore, some sources use an alternative
terminology in which a virus is any form of self-replicating malware.
       The term comes from the term virus in biology. A computer virus repro-
duces by making, possibly modified, copies of itself in the computer’s memory,
storage, or over a network. This is similar to the way a biological virus works.
Some viruses are programmed to damage the computer by damaging programs,
deleting files, or reformatting the hard disk. Others are not designed to do any
damage, but simply replicate themselves and perhaps make their presence
known by presenting text, video, or audio message. Even these benign viruses
can create problems for the computer user. They typically take up computer
memory used by legitimate programs. As a result, they often cause erratic be-
havior and can result in system crashes. In addition, many viruses are bug-
ridden, and these bugs may lead to system crashes and data loss.
       There are many viruses operating in the Internet today, and new ones are
discovered every day. The first PC virus was a boot sector virus called Brain,
created in 1986 by two brothers from Pakistan. The brothers reportedly created
the virus to deter pirated copies of software they had written.
       Before computer networks became widespread, most viruses spread on
removable media, particularly floppy disks. In the early days of the personal
computer, many users regularly exchanged information and programs on flop-
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