
Following Stratio-Zip by a long way is Netsky-P, which is then followed by Bagle-Zip. Zafi-B is in fourth place, followed by Netsky-D, Nyxem-D and MyDoom-O. Eighth place goes to Mytob-C, then Sality-AA and Zafi-D is in tenth.
"No operating system is 100 per cent secure as a standalone system, as end users utilise various alternative applications such as independent email clients, instant messaging, file sharing and more that open new doors for hackers," said Ron O'Brien, senior security analyst at Sophos.
"While Microsoft should be commended for the huge security improvements offered by Vista, every organisation should supplement their systems with compatible technology that defends against hackers at all entry points.
"It won't be long before cyber criminals develop Vista-specific malware or modify current threats to fit the bill. The Stratio-Zip worm, for example, remains on the top 10 list due to constant, minor alterations to its code that force security systems to re-identify the malware," added O'Brien.