Malware reports

Virus Top Twenty for October 2003

Kaspersky Labs presents the twenty most widespread viruses for October 2003

Position Change Virus Name Percentage by Occurrence
1 + 1 I-Worm.Swen 70.94%
2 + 4 I-Worm.Tanatos 1.13%
3 = I-Worm.Mimail 1.07%
4 + 4 Worm.Win32.Lovesan 0.89%
5 + 6 Backdoor.SdBot 0.70%
6 new I-Worm.Sober 0.63%
7 + 2 Worm.P2P.SpyBot 0.59%
8 – 7 I-Worm.Sobig 0.52%
9 new Backdoor.Ciadoor 0.47%
10 + 3 VBS.Redlof 0.39%
11 re-entry TrojanDropper.Win32.Small 0.38%
12 new Backdoor.Agobot 0.30%
13 – 3 Win95.CIH 0.29%
14 + 4 Backdoor.Optix.Pro 0.28%
15 new TrojanProxy.Win32.Hino 0.23%
16 re-entry Backdoor.IRCBot 0.23%
17 – 3 Win32.Parite 0.22%
18 new Keylogger.Win32.PerfectKeyLogger 0.21%
19 re-entry Macro.Word97.Flop 0.18%
20 re-entry Trojan.Win32.StartPage 0.18%
Other Malicious Programs* 4.52%
*not included in the Top Twenty



Malicious Program Types




The October Virus Top Twenty has brought some unexpected surprises.

Firstly, the list has dropped the the Klez and Lentin Internet worms, which have been mainstays on the Virus Top Twenty list since November 2001 and March 2002 respectively. Additionally, the Sobig Internet worm that has occupied the top spot over the past several months has dropped drastically from first to eighth position.

Currently, a newcomer – the worm Swen, appearing just one and one half months ago in mid September, occupies the top spot. In fact, Swen dominates the list by claiming over 70% of all registered incidences, while its closest rivals, the Tanatos and Mimail worms accounted for just over 1% each.

Another unexpected occurrence in October is the significant growth in the number and variety of Trojan programs appearing. An impressive total of nine malicious programs belonging to the Trojan family made the list. In aggregate, Trojan programs well over doubled the total turned in by computer viruses – 6.46% to 2.77%.


  • New malicious programs appearing in the October list are: Sober, Ciadoor, Agobot, Hino, PerfectKeyLogger
  • Moving up are: Swen, Tanatos, Lovesan, SdBot, Spybot, Redlof, Optix.Pro
  • Moving down are: Sobig, CIH, Parite
  • Returning to the list are: Small, IRCBot, Flop, StartPage
  • Holding firm at its previous position is the Mimail Internet worm in third

Virus Top Twenty for October 2003

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