A very dangerous spam campaign is currently in progress as security company Sophos discovered a considerable amount of unwanted messages sent to German Internet users. According to Sophos, the unsolicited emails are containing an attached PDF file named sexy_ganja_report.pdf that encourages users to invest in a company called Talktech Media. The spammers are claiming that they will offer a certain part of the profit to the investors to make the message more attractive.

"Internet users without anti-spam protection are probably used to seeing messages in their inbox telling them to buy shares in companies they've never heard of, but usually the promotions are in the form of regular text or an embedded image," said Graham Cluley, senior technology consultant for Sophos.

At this time, there is no 100 percent efficient solution to block the spam messages coming into your inbox, although some of the software companies are claiming that their products can assure the protection of the attacked computers. The PDF attachments are even more dangerous because until now, the spam campaigns contained only executable files.

"In an attempt to get past anti-spam filters criminals are now using PDF file attachments to carry their slick enticements for people to invest. The positive news is that a good anti-spam defense can protect against this nuisance, but the rewards for this kind of crime mean that spammers are unlikely to stop their pump-and-dump scams anytime soon."

As usual, you're encouraged to avoid opening untrusted emails and to refuse clicking on the messages that contain PDF files. In addition, you can configure your account to block the unsolicited emails after the spam messages appeared in your inbox. Obviously, nobody is 100 percent safe when it comes to unsolicited emails but, if you want to protect yourself, the best way is to refuse opening them.