FORTUNE — As the credit card wars heat up, four little-known upstarts — Advanta, Capital One, First USA, and MBNA — are using information technology to charge ahead of the competition. The quartet, which issue Mastercards (MA) and Visa (V) cards, have been poaching the most profitable customers from the traditional bankcard issuers.

Advanta, Capital One, and First USA use sophisticated information systems to target the most profitable customers — cardholders who maintain sizable loan balances but never miss a payment. While most credit card issuers indiscriminately blanket the country, offering new cards to millions of names in a database, these three identify the best prospects. They lure their prey with direct-mail or telephone pitches offering low introductory teaser rates of around 5.9%. New customers are not clinched, however, until those introductory rates expire. That’s when the issuers’ computers mail the customers individualized offers with rates as low as 13.9%, vs. a national average of 17%. The trio can afford these bargain-basement prices because their customers are more profitable than the competition’s.

The niche carved out by MBNA is different but also relies on flexible information systems. This company is the king of affinity cards. It has mastered the art of signing up folks who want to bond via credit cards with others who share their passions, be they classic cars, the Chicago Bulls, or the Billfish Foundation. By issuing cards linked to more than 4,000 organizations, MBNA has 16 million customers, making it the No. 3 player behind Citibank and Discover (DFS).

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