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The infamous Klez worm has retained the top spot in security firm Sophos's most frequently occurring viruses table for the fifteenth month in a row, while 475 new viruses were discovered in April.

Two old favorites also reared their heads again--Lovegate-E and Funlove--spreading concern that individuals and companies are not keeping their antivirus software and firewalls up-to-date.

"It's no good installing the software if it's not maintained," says a Sophos spokesperson.

A new virus called Datemake Dialler also made its way into the top ten. The malware, known as a dialer, is programmed to dial a premium-rate telephone line, typically with the intent of gaining access to adult material.

"Businesses should apply strict computing guidelines to avoid getting stung by a huge telephone bill and embarrassed by these seedy programs," says Graham Cluley, senior technology consultant at Sophos.

Still Spreading

Top viruses were:

1. W32/Klez-H, 12.7 percent of complaints

2. W32/Lovgate-E, 4.9 percent

3. W32/Bugbear-A, 4.3 percent

4. W32/Sobig-A, 3.3 percent

5. W32/ElKern-C, 2.9 percent

5. W32/Yaha-E, 2.9 percent

5. W32/Yaha-K, 2.9 percent

8. JS/NoClose, 2.1 percent

9. W32/Flcss, 1.9 percent

10. Dial/Datemake-A, 1.6 percent

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