VIRUS !!!

today, i will tell you all about virus..we know that, many of virus that can we found and the popular virus is called 'TROJAN'..

WHAT IS A VIRUS???

A computer virus is a small program written to alter the way a computer operates, without the permission or knowledge of the user. A virus must meet two criteria: 

1) It must execute itself. It often places its own code in the path of execution of another program.

2) It must replicate itself. For example, it may replace other executable files with a copy of the virus infected file. Viruses can infect desktop computers and network servers alike.

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 to replicate themselves and make their presence known by presenting text, video, and audio messages. 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 behavior and can result in system crashes. In addition, many viruses are bug-ridden, and these bugs may lead to system crashes and data loss.

WHAT IS A TROJAN HORSE???

Trojan horses are impostors—files that claim to be something desirable but, in fact, are malicious. A very important distinction between Trojan horse programs and true viruses is that they do not replicate themselves. Trojan horses contain malicious code that when triggered cause loss, or even theft, of data. For a Trojan horse to spread, you must invite these programs onto your computers; for example, by opening an email attachment or downloading and running a file from the Internet. Trojan. Vundo is a Trojan horse.