The Storm worm proved to be the number one malware threat of 2007, topping BitDefender's list of the 10 most prevalent offenders of the year.

Also known as 'Peed bot' and 'Nuwar', Storm clocked up 33.94 per cent of total detections over the past 12 months placing it well ahead of its Trojan rivals.

The rogues' gallery of malware includes numerous mass mailers, including the Netsky family with three separate entries. This makes Netsky.P the most harmful and long-lived mass mailer of all time, according to BitDefender.

Sality.M was named as the most underrated threat of the year, which BiDefender describes as "a highly dangerous polymorphic virus spread via mail and other means".

Virtob.2 was 2007's "most spread" file-infecting malware. Although relatively harmless, Virtob.2 has a tendency to infect the same files many times over.

"The past year has seen the tail end of the mass mailer and the rise of the botnets as the top threat category," said Viorel Canja, head of BitDefender's Antivirus Lab.

"BitDefender's top 10 for 2007 also reflects a re-emergence of file infectors as a credible threat, primarily because of widespread P2P sharing. We will see what the future holds."

BitDefender 2007 Top 10 malware list:

1. Trojan.Peed.Gen (Storm) 33.94%
2. BehavesLike:Trojan.Downloader 24.86%
3. Win32.Netsky.P@mm 6.49%
4. Trojan.Peed.A 2.13%
5. Win32.Nyxem.E@mm 2.13%
6. Win32.Sality.M 2.06%
7. Win32.NetSky.D@mm 2.06%
8. Win32.Virtob.2.Gen 1.60%
9. Win32.Netsky.AA@mm 1.49%
10. Trojan.Peed.P 1.17%