What is a computer virus?
Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation without your knowledge and runs against your wishes. A computer virus that can make a copy of itself over and over again is relatively easy to produce. A virus might corrupt or delete data on your computer, use your e-mail program to spread itself to other computers, or even erase everything on your hard disk.
A computer virus exhibits two characteristics:
- They are self executing. Typically, a virus will attach itself to another programme on your computer, so that it is activated when that programme is used
- They are self-replicating. Computer Viruses are designed to spread from machine to machine and across networks. To achieve this, a virus will usually copy itself to other programmes on a computer, before executing any intended tasks.
The term “computer virus” is derived from and is in some sense analogous to a “biological virus”. Computer viruses have similarities with biological virus. Both of them need a host for residence. In the case of computer virus, the host is usually the infected file, e-mail or disk. Both of them are capable of self-replication from one host to another. Both of them may cause damage to the host. The difference is that computer viruses are created by human while biological viruses are not.
Viruses are most easily spread by attachments in e-mail messages or instant messaging messages. That is why it is essential that you never open e-mail attachments unless you know who it’s from and you are expecting it. Viruses can be disguised as attachments of funny images, greeting cards, or audio and video files. Viruses also spread through downloads on the Internet. They can be hidden in illicit software or other files or programs you might download.
Computer viruses have impacted a significant number of computers over the past few years. There are currently over 10,000 known computer viruses worldwide. Over 200 new viruses are being discovered every month.
Viruses are sometimes confused with computer worms and Trojan horses. A worm can spread itself to other computers without needing to be transferred as part of a host, and a Trojan horse is a file that appears harmless until executed.