The number of new malware threats doubled in September, new figures show.
Statistics released by security company Sophos show 4,080 new threats compared to just 1,998 in October.
The overall level of infected email, however, dropped to an all time low of just one in 300.
Sophos explained that this shows cyber-criminals moving away from mass-mailed attacks in favour of more subtle and menacing attacks targeted at a small group of users.
The report, compiled from Sophos' global network of monitoring stations, revealed that Netsky-P continues its domination at the top of the charts, with the top five most prevalent pieces of malware retaining their position from last month.
There were no new entries in September's chart and just one re-entry:
"Internet criminals have had a busy September, producing twice as many new threats as they did in the previous month," said Graham Cluley, senior technology consultant at Sophos.
"The new malware we are detecting can be much more sinister than the old timers that dominate the chart. It often aims to steal sensitive data and information which can be extremely damaging to a company's reputation and bottom line.
"We recommend that all organisations put in place a consolidated security solution that protects against known and unknown malware threats."
The top 10 list of malware in September 2006
1. Netsky-P (18.4 per cent)
2. Mytob-AS (14.1)
3. Bagle-Zip (6.3)
4. Nyxem-D (5.4)
5. Netsky-D (5.3)
6. Mytob-E (3.0)
7. Mytob-C (2.9)
=8. Zafi-B (2.8)
=8. MyDoom-O (2.8)
10. MyDoom-AJ (2.7)
The top 10 hoaxes and chain letters in September 2006
1. Olympic torch (8.5 per cent)
2. Hotmail hoax (8.2)
3. WTC Survivor (7.9)
4. Bonsai kitten (4.5)
5. MSN is closing down (4.1)
6. Bill Gates fortune (3.2)
7. Meninas da Playboy (3.0)
8. Justice for Jamie (2.6)
9. A virtual card for you (2.5)
10. Budweiser frogs screensaver (2.0)
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