Virus top 10: Is Klez the Bryan Adams of the virus world?

The Klez worm has topped the virus charts for the fourth month running,

According to the latest statistics from US anti-virus specialist Central Command, the worm has now managed to infect over one million computers worldwide.

Klez has several variants, which were first identified last November, but the two versions currently doing the rounds are the E and G strains.

The worm spreads as an email attachment and uses a variety of subject lines. The E and G variants destructive features such as time-activated payloads, which trigger the worm on a specific day of each month.

The Klez-H variant is also capable of carrying other viruses such as Elkern, which it then automatically launches once the attachment is executed.

Elkern appears in second place in this month's chart for this reason.

Further down the list, the Sircam virus is still infecting PCs, as are variants of old favourites Nimda and Magistr. The Badtrans worm is also continuing to plague IT systems worldwide.

A new entry for June is Yaha, a virus that was only discovered in late May. The worm arrives as an email attachment with varying subject lines, many related to romance.

Here's the full month's list from Central Command:
1. Worm/Klez.E (includes G,H variant) 60.2%
2. W32/Elkern.C 24.5%
3. Worm/W32.Sircam 3.9%
4. W32/Yaha.E 2.6%
5. W32/Nimda 2.3%
6. W32/Magistr.B 1.9%
7. Worm/Frethem.D 1.6%
8. Worm/Badtrans.B 0.7%
9. W95/CIH 0.4%
10. W95/Hybris 0.4%