Spammers have decided to kill two birds with one spam: The stock-touting e-mail messages regularly sent out by spam-focused bot nets have started to include links to malicious code, according to a report published Wednesday by e-mail security firm MessageLabs.

The criminal groups responsible for the spam appear to believe that recipients of the e-mail may click on a Web link, even if they don’t buy the stock touted by the e-mail message. In the past 10 days, MessageLabs has only detected about 3,500 of the messages, so the spammers may be testing to waters to see how often the scam works, said Mark Sunner, chief technology officer for the company.