Bugbear accounted for almost 30 per cent of all reports of malware to Sophos in the last month - well ahead of former top spot incumbent Klez which now only accounts for around eight per cent of all reports in third place.
Also making headlines, straight in at number two, is the Braid worm with 8.5 per cent of all reports.
Graham Cluley, senior technology consultant at Sophos, said: "Bugbear dominates the chart for the second month as it continues to out-fox users with its dual mode of attack. This worm can spread via email and network shares.
"It's important that all users ensure they are protected against Bugbear because it implants code that can log victims' keystrokes. This means hackers have a perfect view of everything you type - this could include passwords, bank account details and credit card numbers."
The Top 10 in full (figures represent total percentage of all virus reports attributable to each virus):
- W32/Bugbear-A (Bugbear worm) 29.4 per cent
- W32/Braid-A (Braid worm) 8.5 per cent
- W32/Klez-H (Klez variant) 7.7 per cent
- W32/Opaserv-A (Opaserv worm) 5.4 per cent
- W32/Opaserv-C (Opaserv variant) 5.1 per cent
- W32/Flcss (FunLove worm) 4.6 per cent
- W95/Spaces (Spaces virus) 3.3 per cent
- W32/Opaserv-F (Opaserv variant) 2.5 per cent
- W32/Opaserv-B (Opaserv variant) 2.1 per cent
- W32/Opaserv-D (Opaserv variant) 2.0 per cent
