According to mi2g Intelligence Unit, about 115 million personal computers in 200 countries were infected throughout 2004. Approximately eleven million PCs become zombis and without their owners' knowledge are used to disseminate spam and fishing, start Dos-attacks or spread new viruses.
In the opinion of Kaspersky Laboratory analysts, some 2004 viruses - Sasser, Padobot, Bobax - made use of system vulnerabilities as the only method of attack, spread through the Internet from computer to computer absolutely ignoring the "customary" methods. Other harmful programs, such as Plexus, as well as numerous versions Bagle, Netsky and Mydoom, combine the use of loopholes in the operational systems with other contamination methods (mass distribution, use of network resources, P2P technology).
