The Trojan virus is the most famous computer virus around the world. The virus allows a hacker to have a remote access to a targeted computer system. Basically, you have given him a free pass or free access to passwords, downloads, credit card numbers and personal information.

With thousands of bank accounts compromised, this virus could very well top the list of the most damaging virus globally.  However, there are far more dangerous viruses that have been circulating the net for the past decades.

Conficker virus – this was also known as downup. A computer worm, believed to be the largest computer infection since 2003. It affected seven million government businesses and home computers in 200 countries. This virus penetrated the armed forces of France and Britain infecting defense systems. “Downup” also contained mechanisms that deploys payload.

Melissa virus – known as the Simpson virus, it was originally designed not to harm. However, it overloaded servers and caused problems. And that problems cost an estimated damaged of about $1 billion. The virus used a mass e-mail process sending 50 entries to affected user’s address book in Microsoft outlook. It would randomly insert quotes from “the Simpsons” series and delete crucial windows files.

Code Red virus – Code Red was computer worm virus that attacked computers running Microsoft’s IIS web server, the worm exploited the IIS vulnerability by buffer overflow. When the buffer overflows it will have so much information sent to an affected computer that causes it to shutdown. It attack a number of government websites with an estimated $2 billion damages. After their initial release, they also launched a code red 2 virus that also wreak havoc to thousands if not millions of computers.

MSblast virus – A computer worm that exploits computers using Windows XP and Windows 2000 in 2003. It was a Microsoft vulnerability that was taken advantage by hackers. It will install a trivial file transfer protocol server which will download codes to the infected host. It has an estimated of $10 billion in damages.

I Love you Virus – This was initially a project made by a Filipino IT student in school. However, when his project was declined, he initially launched the “I love you virus”. It has an estimated of $8.7 billion damages including the most secured of all places the U.S. pentagon. It cleverly uses an email with a subject “I Love You” that disguised as a text file. When the file is open it will automatically detect all the contacts on the users address book then overwrites all your files. The virus is the most successful computer viruses of all time. The author is now believed to be employed in an antivirus company in the U.S.

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