Ever had an e-mail from someone called Sarah Dugan, titled 'Hi'? At first, you might think you know her, but 'Sarah' is promoting a little-known stock from Advanced Powerline Technologies, a company that is expecting a big announcement soon - and you'd be mad not to buy shares. What about an e-mail from Keisha Williams? You don't know 'Keisha' but she is pitching shares in Forest Resources, 'the hot pick for December', and with a five-day target of US$1.50 growth you'd be crazy not to invest. Once it was offers of Viagra, home loans and porn sites that arrived, unsolicited, in your inbox. More recently, phishing spam claiming to be from banks, exiled Nigerian diplomats or singles looking for no-strings-attached sex were the order of the day. But not any more. The newest form of spam comes in the form of share-pushing scams, also known as pump-and-dump e-mails. About 100 million such e-mails are sent out each week, accounting for 15 per cent of spam messages, according to online security firm Sophos. What's more, few pump-and-dump messages are caught by inbox filters. While most people have the good sense to ignore these e-mails, some purchase the promoted stock, which the spammers have already bought into. When others follow suit as a result of the spam, the price soars. An illiquid stock with a low trading volume valued at just US$1 a share only has to snare a few gullible buyers out of the millions contacted to move the price up. The spammers then sell the next day, making a tidy profit. Pump-and-dump scams are very effective, with spammers feeding off the three Gs: greed, gullibility and globalisation. Shares are now so easy to buy online, through legitimate firms such as Pink Sheets, an online trader specialising in small stocks, that being ripped off is just a click away. Most of the pump-and-dump shares never pay dividends and collapse in price when the scammers dump their stock. Few such stocks even manufacture anything, mainly being 'micro-cap' firms - generally US technology start-ups. Many exist just for the scam, part of a never-ending circle of 'PR firms' and spammers. The PR firms promote their spammer clients by getting stories on websites, the spammers then point to the stories. Some of the firms talked about are legitimate and are as much a victim of spammers as the investors. Take one e-mail announcing that Dark Dynamite 'plans to profit from a theme park operating at the Qin E-Pang Palace in mainland China'. It is 'a terrific investment opportunity' at US$1.58 a share. It's odd, however, that Dark Dynamite, a failed clothes manufacturer, should be about to start building theme parks. Days later, the stock fell to 60 US cents a share. So why do we get these spams? Why don't the filters ... erm ... filter them? New technology hijacks home PCs to send out spam. But, crucially, it only sends a few messages from each hijacked PC to avoid being entered on the backlists that filters consult. Such e-mails also break up the key words that spam filters look out for. This is why you get 'V-I-A-G-R-A' messages. Craftier still, pump-and-dump scams are often sent as picture files containing text, rather than as a regular e-mail message. This is why the text is often gibberish or a list of words seemingly cut and pasted from a thesaurus. All this bypasses filters. The human touch is also added. If you get an e-mail from Sarah Dugan saying 'Hi', you will be more likely to open it than one from Viagra Sales Inc. So will pump-and-dump go on forever? Thankfully not - the spammers are a victim of their own success. Investors are now so wary of any stock promoted in spam that they dump their stock immediately, thus hurting the spammers' pockets first.