I've said it before here but now that a professional security specialist is talking about it (see Twitter spammers post sexy profile pictures) people should take notice.

Twitter has not responded to a request for comment but it's still early in sunny California.

Meanwhile, it's obvious that a group of spam bots are using sexy photos to try to lure victims to sign up for a pornography service, according to Sophos security expert Graham Cluley.

"Spammers have created scores of bogus profiles and followed random users en masse. Each of the profiles comes has a sexy picture of a young woman, complete with a message from the spammer embedded inside the image," he wrote in a blog post.

"Trust me, the image I've included below is much cleaner than many of the other ones being used by the spammers. Some of the photos you definitely wouldn't want to share with your mother-in-law," he added.

For the sake of science, he replied to one and ended up on an MSN chat where it soon became clear that a bot rather than a person was trying to get his credit card information for a "free" pornographic chat service.

He said that the spammers are evading Twitter's filters by using image spam, a common spam technique, according to Cluley and also according to reports from Google and MessageLabs.