The mass-mailing worm, Sober.K, is currently the third most commonly encountered virus, making up 10 percent of all viruses detected in the last 24 hours, Sophos reported.
"This latest variant of the Sober worm may catch out the unwary as they open their e-mail in-box," said raham Cluley, senior technology consultant at Sophos.
"Although much-publicized virus outbreaks in the past should have made users more nervous of double-clicking on unsolicited e-mail attachments, some still find it hard to resist," he added. "All users should be reminded to follow safe computing guidelines, and PCs should be kept automatically updated with the latest antivirus protection." The new Sober variant sends itself in German and English, using a variety of subject lines, including "Paris Hilton, pure!" and "Paris Hilton SexVideos."
The Zafi.D virus, which was released last year, is Sophos' most prevalent, accounting for 27.6 percent of all reports in the last 24 hours. The Harry Potter Netsky.P worm is in second position with 22.4 percent.
Hilton shot to prominence after starring in a home video that became an Internet phenomenon. On the same day that Sober.K was discovered, it was reported that hackers had broken into Hilton's cell phone and stolen the telephone numbers of celebrities before posting them online.
A second, more dangerous worm that uses similar bait, Ahker.C, was also discovered this week. The Ahker-C worm disables antivirus and firewall settings, and blocks access to some Web sites. It sends itself with the subject line "Paris Hilton...download it!" and a file called "ParisXXX.zip", which contains the virus.
Dan Ilett of ZDNet UK reported from London.