A new and improved botnet is using the upcoming Valentine's Day holiday to spread malware through phony greeting cards and romance-themed emails.

A senior researcher with Eset, Pierre-Marc Bureau said he expects Waledac, the improved version of former botnet Storm, to send out thousands of Valentine's a day. He told Dark Reading: "Over the last 24 hours, we've seen over 1,000 new variants [of Waledac code]."

The industry website said that the security threat is coming in many forms, with one of the latest attacks appearing to be a puppy love e-card accompanied with a Valentine's-related link.

The website warns that subject lines for the emails include the fairly obvious "a Valentine card from a friend" but once users click on the link to receive the message, malware is downloaded onto the computer.

Another attack uses pop-up ads to direct users to download fake antispyware software that infects the machine.

Ryan Sherstobitoff, vice president of Panda Labs, warns: "The authors have started adding supposed magazine endorsements and other elements that one would see on a reputable anti-malware site. The graphics within the pop-ups themselves seem to be professionally designed at this point, so it is very critical for users to treat email from unknown persons with extreme caution."

The news about the Valentine's Day spam follows a warning from experts earlier this year saying that the creation of new botnets could lead to higher levels of spam during 2009. Four prominent botnets were dismantled last year, but since then new bots that are harder to bring down has been taking their space.

Valentine spam sparks security warnings