For example, a spammer who owns 1,000 shares in a company sends out an e-mail saying "buy these shares, they're about to really take off" and if enough people are tempted it not only become a self-fulfilling prophecy but it makes them a tidy packet in the process.
According to UK mail filtering firm Clearswift, financial spam now accounts for 26 per cent of all unsolicited e-mail, second only to healthcare (57 per cent).
Alyn Hockey, product director at Clearswift, said: "The only conclusion we can draw is that these people are doing this for their own financial gain."
The tactic also shows a maturing in spammers' techniques. They no longer need to make a sale or elicit a response - they simply need to tempt enough people to chance a flutter on a resurgent stock market.
Hockey says such scams may succeed because they play upon people's greed. "And there will always be greedy people out there," he added.
However, even those who are aware that these e-mails are spam may believe that they are likely to become self-fulfilling prophecies and thus follow the 'buy' recommendation - in expectation of enough people being duped and the share price rising accordingly.
After all, the spammers are obviously convinced that this will make them money, so many people may adopt a 'why shouldn't I' philosophy.
Many people receiving legitimate share tips and trading advice, which makes it far harder to filter out the spam. Hockey said: "You hate to say it, but you have to admire the intelligence of these people. If they can send these e-mails to enough people and make it look like genuine stock news feed then not only will they evade a lot of filters but they may also fool a lot of people"
In related news, Clearswift today reported that 55 per cent of companies believe their anti-spam measures are inadequate.
Issues with false-positives and huge quantities of spam still getting through are the most common problems faced - although 72 per cent of firms do now have spam filtering tools in place, according to the firm.
