Security: That PC's a Rogue.

Byline: Benjamin Sutherland

When an identity thief fleeces a financial firm or retailer with stolen credit-card numbers, there's no stopping the fraudster from returning to the Web site armed with yet another stolen identity. Now companies are trying to make it that much harder by tagging the thief's PC with "device reputation" software.

The software runs on a company's Web site, capturing the serial number and other hardware "fingerprints" of any PC that logs on--when a user clicks on a page, purchases a product or places a bet. If the transaction turns out to be fraudulent, the PC's fingerprint is added to a database of computers with bad reputations. Subscribers to the service, offered by Portland, Oregon-based iovation, are alerted every time a dubious PC shows up to do business. So far 30 companies in 11 countries in North America and Europe have joined iovation's "Reputation Manager" network. Once a firm is ripped off, the whole group is protected. "They have to suffer some pain to identify a problem," says iovation CEO Jon Karl, "but they only have to get hit once."

The database sorts PCs into 20 categories, which range from the use of profanity in online forums to outright fraud. ...