Well-known malware threats and hoaxes continue to head the list of the most reported online problems, despite a government campaign designed to educate users.
"On the one-year anniversary of Get Safe Online, established virus families such as Netsky, Mytob and Zafi continue to cause havoc for UK internet users, despite protection having long been available," said Sophos.
The well-known Netsky-P was the most prevalent piece of malware in circulation, although variants of the Stratio worm have entered the top 10 for the first time.
Sophos said that several hundred variants of Stratio were widely spammed out during October, accounting for more than 50 per cent of all reported malware on some days.
The proportion of infected email remains low, at just one in 300, while Sophos identified 3,076 new threats during October.
"This is like a new dog employing old tricks," said Carole Theriault, senior security consultant at Sophos.
"Stratio has made it into the top 10 because it uses numerous social engineering tactics and has been aggressively spammed out."
Theriault added that home users who have not installed or updated their anti-malware protection remain the most vulnerable targets.
She also warned that, if old-timers like Netsky and Mytob are still getting through users' defences, new malware is probably doing the same thing.
"Given these circumstances we have to ask whether the Get Safe Online campaign is really having the intended impact," said Theriault. "We are still awaiting firm evidence that it has actually connected with the general public."
Sophos top 10 malware threats in October 2006:
1. Netsky-P 15.2%
2. Mytob-AS 12.2%
3. Stratio-Zip 5.7% new entry
4. Bagle-Zip 5.3%
5. Netsky-D 5.1%
6. Stratio-AY 4.3% new entry
7. Mytob-C 3.5%
8. Zafi-B 3.4%
9. Nyxem-D 3.1%
10. Mytob-E 2.6%
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Malware has been in circulation for more than a year