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Top Viruses for 2004

In the year that is coming to an end, the Downloader.GK Trojan has been the malicious code that has caused most damage among users’ computers, according to the data gathered by Panda ActiveScan. The prevalence of this Trojan signifies an important change in the repercussions that malicious codes are having on users’ computers, as until now, first place in this annual ranking had always been occupied by a worm.

Panda Software’s ActiveScan is a free virus removal tool available for all computer users to repair their computers and fix the viruses missed by other antivirus providers.

Data provided throughout 2004 demonstrates Downloader.GK ranks #1 for 2004 and responsible for approximately 14% of all attacks. This Trojan doesn’t spread of its own accord, but is downloaded onto computers when unsuspecting users visit certain web pages and accept the installation of a specific ActiveX control. Downloader.GK installs and runs two adware programs on the computers it infects. More information about Downloader.GK can be found at:

The remainder of the Top Ten ranking of malicious code detected by Panda ActiveScan was comprised of:

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%)

The following conclusions can be drawn from the data collected by Panda ActiveScan during 2004:


Since it first appeared in June 2004, Downloader.GK has been the malicious code responsible for most attacks on users’ systems, replacing worms as the primary threat and heralding the advent of a dangerous new trend in malware, as the impact of Trojans is on the increase. This is also manifest in the fact that four of the Top Ten are also Trojans, when in 2003 there were two, and in 2002 just one.

THE PRESENCE OF NETSKY Three of the Top Ten ranking are members of the Netsky family, (the P,B and D variants). The three share a number of characteristics, and as with many worms, they all spread via email in messages with variable characteristics.

VULNERABILITIES IN THE LINE OF FIRE Four of the malicious code in this year’s Top Ten use vulnerabilities in common software installed on computers in order to carry out their malicious action. This highlights the danger that these flaws represent and the need for users to install the patches provided by vendors to fix them.

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