The Downloader.GK Trojan was responsible for 14% of all attacks on computer systems spotted by antivirus software maker Panda Software in 2004--more than double the attacks of any other virus this year.
The Downloader.GK Trojan infects Web surfers who unknowingly visit Web sites that were maliciously designed to spread it. Users are enticed to install a specific ActiveX application, which secretly installs spyware and adware on their systems.
2004 is the first year a Trojan horse--a malicious application that doesn't spread on its own like traditional viruses or worms--topped Panda's annual threat list. What's more, four out of the top 10 threats the company tracked this year were Trojan apps.
Virus attacks in 2004 could prove to be the costliest ever, according to the research firm Computer Economics. In September, the firm projected the financial impact of major virus attacks for the year to reach $17.5 billion. That tops the previous $17.1 billion high in 2000, and surpasses the $13.0 billion figure reached in 2003.
Below are the remaining top 10 threats Panda tracked, followed by the percent of attacks they were responsible for:
2. Netsky.P (6.92%) 3. Sasser.ftp (4.97%) 4. Gaobot.gen (4.31%) 5. Mhtredir.gen (4.22%) 6. Netsky.D (3.98%) 7. Downloader.L (3.56%) 8. Qhost.gen (3.48%) 9. Netsky.B (3.45%) 10. StartPage.FH (3.34%)