Netsky and Sasser Worlds Deadliest Virus

A computer virus is a type of malware that, when executed, replicates by inserting copies of itself (possibly modified) into othercomputer programs, data files, or the boot sector of the hard drive; when this replication succeeds, the affected areas are then said to be "infected".^[1][2][3] Viruses often perform some type of harmful activity on infected hosts, such as stealing hard disk space or CPUtime, accessing private information, corrupting data, displaying political or humorous messages on the user's screen, spamming their contacts, or logging their keystrokes. However, not all viruses carry a destructive payload or attempt to hide themselves—the defining characteristic of viruses is that they are self-replicating computer programs which install themselves without the user's consent.

Netsky and Sasser Worlds Deadliest Virus

By 2004, virus writers were rapidly exploiting and building on each other's code, so much so that they were 

beginning to interfere with one another. So the Netsky and Sasser worms took the extraordinary step of 

attempting to clean out other worms on a victim's PC before installing themselves.

Sasser drew attention because it knocked out the satellite communications system for the French news agency 

Agence France-Presse and caused problems with Delta Air Lines systems, causing some flight cancellations. 

Eventually, both viruses were traced to a teenage computer science student in Germany....