Today's scam introduces a character whom we have not yet dealt with here -- the online stock operator.

Long before the invention of the Internet, some unscrupulous person discovered that he could make money by buying a large number of shares of a cheap stock, hyping the company, then selling the stock for a profit to folks who fall for the hype. This type of scheme is known as a "pump and dump" -- as in pump up the price, then dump the stock.

When this person's moral descendants learned how to use e-mail. they began bombarding hapless recipients with messages proclaiming that the stock of some company or another was poised to break out, and might reach a price as high as a dollar (the stocks being hyped are usually penny stocks.) Like most online scammers, these operators count on the sheer volume of e-mails sent to produce the desired results -- namely that enough people would decide to buy the stock that the momentum does indeed drive the price up.

As software developers created spam filters, the spammers found ways to get around them, such as deliberately misspelling words or inserting chunks of nonsensical text into their messages. As Dan Clements, president of CardCops.com, a site that monitors online fraud, told MSNBC, "If you put up a 10-foot wall, they're going to find an 11-foot ladder."

In recent weeks, the 11-foot ladder has been e-mail attachments rendered as .PDF (Portable Document Format) files. Because spam filters look for text, a .PDF, which is an image, will slide right through. And slide through they have, creating a surge of spam. Typically, such an e-mail does not even have a message within the body of the e-mail itself, only an attachment like this one, received last week:

Vision Airships Global Expansion!

BANKGKOK, THAILAND, Jul 09, 2007 (MARKET WIRE via COMTEX) -- Vision Airships Inc. (PINKSHEETS: VPSN) -- The company wished to announce that is has finalized arrangements for funding for its global expansion.

Vision Airships is set to become a worldwide operator of blimps used for advertising around the world. As the advertising market gets more crowded in conventional mediums -- the use of alternative forms of advertising is gaining more and more traction -- this is where Vision Airships comes in and supplies the end to end solution to major advertisers worldwise with its unique form of alternative displays. The size of the market worldwide will support 24 airships which would bring in approximately $400,000,000 annually.

Check out the news and get on VPSN first thing Tuesday and Wednesday!

This particular e-mail didn't work, by the way. VSPN shares dropped both Tuesday and Wednesday of last week, then dropped further on Friday.

The e-mails that merely have a PDF attached do not pose a real danger. But some e-mails combine the "pump and dump" with phishing, containing links designed to acquire information about the recipient's brokerage account. Once a scammer has that information, he can use the victim's account to buy the very stock that they're hyping.

So if you receive an e-mail with nothing but an attached .PDF touting a penny stock poised for a breakout, delete it. If you receive one with such a .PDF and links to a Web page ... delete it.