Antivirus experts have upgraded the Klez virus status to severe. Symantec, an anti-virus vendor has reported the virus has affected “a few thousand” in just one day. The Klez virus has proved to be one of the more sever viruses lately seen. Symantec reports to have identified approximately 3,000 infections a day. In comparison, Sircam (when at its peak) only infected 1,500 in one day.

The latest variant of this worm is difficult to detect as it spreads with a random subject line, message and attachments. Once opened the worm will search through Windows address book, ICQ database, and local files for email address’ and then mail itself to those address found. Kelz is even harder to detected as it will appear as being from one of the email address found in the address book.

Security experts warn the virus may attempt to delete files in the local drive on 13th September or 13th March.

Click here for a patch and information about this vulnerability.