W32/Lirva.C@mm was not in the first place as F-Prot AVES' most stopped virus for long as W32/Klez.H@mm took its place after less than two days.

As can be seen from the chart below, this is not because of a great increase in the distribution of Klez.H, but rather due to quite some fluctuations in the distribution of W32/Lirva.C@mm. Klez.H has on the other hand been rather stable in its spread since it appeared last year, and does not seem to be disappearing.

Comparison of the distribution of W32/Lirva.C@mm and W32/Klez.H@mm in January, measured at 24hour intervals. W32/Lirva.C@mm shown in pink and W32/Klez.H@mm marked with dark-blue

We urge computer users to keep their antivirus software up-to-date.

As W32/Klez.H@mm is an old virus since April last year it is known and detected by most antivirus software. The reason for its continuous distribution is therefore most likely because of computer users using outdated antivirus software or none at all.