Netsky.P remains in the number one position for malware infections, accounting for over 24 percent of PC infections, but has stiff competition in the form of Zafi.B, which was first released in June. But Zafi may be loosing its position in favour of some newer variants of some old baddies.

Two new viruses have emerged in the last month which caused concern. A new variant of Sober, Sober.I, first appeared on the 19th of November and has overtaken Zafi.B at second place. Also new is new Bagle variant Bagle.AU, which is at 4th place. These new viruses have jumped straight into the top 5.

Currently, the top ten list of most prevalent viruses is as follows:

1. Netsky.P 24.2 per cent
2. Sober.I 20.4 per cent
3. Zafi.B 17.9 per cent
4. Bagle.AU 11 per cent
5. Netsky.D 4.4 per cent
6. Netsky.Z 3.9 per cent
7. Bagle.AA 2.6 per cent
8. Netsky.B 2.4 per cent
9. MyDoom.O 2.2 per cent
10. Netsky.Q 2.1 per cent

According to antivirus firm Sophos, a key to virus success lies in its social engineering - how well it fools the user into doing what it wants and how well it appears to be something far less nasty. Worms such as Sober encourage recipients to open an attachment by claiming it contains important security or messaging information.