Some examples of computer viruses include the Storm Virus, Sasser Virus and Melissa Virus. A computer virus is a program that causes some sort of harmful activity to a computer and then attempts to replicate and spread itself to other computers.
The Storm Virus originated in 2007, spreading itself through a supposedly informative email detailing a disastrous storm that had killed hundreds. Clicking the news link would direct users to a site from which the virus would automatically download. The Storm Virus changed its headline to match current events, but its purpose always remained the same.
The particularly malicious Sasser Virus emerged in 2004, disabling the computer systems of the British Coast Guard, Agence France-Presse and Delta Airlines, among others. Numerous other corporations, hospitals and universities were infected with the Sasser Virus, which caused computer systems to repeatedly crash. The creator of the virus turned out to be Sven Jaschan, a German teenager who was sentenced to 21 months of probation and community service for his role in distributing the virus.
The infamous Melissa Virus was the first worm to be spread through email attachments, ushering in a new era of computer viruses. Melissa was also one of the first viruses to access users' email address books and send itself to all the contacts contained within, a practice that continues to this day.