The fraudsters behind pump-and-dump stock spams are trying a new technique in a bid to fool spam filters. Junk mails promoting worthless stocks seen this week are appearing with an attached PDF file.

Typically titled "German Stock Insider", these PDF files purport to offer insider tips and contain more detail than is generally the case in typical pump-and-dump scams, even going to the bother of adding logos and the like for added "authenticity".

They even contain a disclaimer to make them more closely resemble genuine stock prospectus guides. This disclaimer typically reads: "This is not an offer to buy or sell any security. German Stock Insider discloses that they were paid ten thousand Euros for distribution of this report."

Pump-and-dump scams are email campaigns that seek to encourage armchair investors to sink their cash into particular firms' stock.

The goal is to quickly inflate interest in low-value stock with bogus insider info in order to ramp up share prices and sell at a profit before the inevitable crash and burn. Meanwhile, those duped are left holding possibly worthless shares.

Most (but by no means all) of these scams are thought to take place without the knowledge of firms that are the subject of the scams.

According to net security firm Sophos, pump-and-dump stock campaigns account for approximately 25 per cent of all junk mail, up from 0.8 per cent in January 2005.

Content security firm Marshal, however, reckons the tactic is in decline after reaching its high-water mark in February. One in two junk mails scanned by the Australian firm in February involved pump-and-dump scams, a figure that nose-dived to just five per cent in June, according to Marshal's figures.

Earlier this year, the US Securities and Exchange Commission (SEC) suspended trading in 35 firms as a punishment after the companies were frequently referenced in pump-and-dump stock email campaigns. ®

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