Computer hackers went after a big fish during the weekend, stealing credit card information belonging to 19,000 customers of AT&T Inc., officials said Tuesday.

The thieves hacked into a site that sells DSL equipment used by high-speed Internet customers. AT&T shut down the site and immediately took steps to notify the customers and protect them from identity theft, spokesman Walt Sharp said Wednesday.

"Everyone will get a letter," Sharp said. "The majority already have gotten an e-mail, and those for whom we did not have an e-mail address, there are phone calls being made."

Although he offered no geographic breakdown, Sharp said Oklahoma customers were almost certainly among those whose information was pilfered.

The company will pay for credit monitoring and is suggesting customers contact their credit card companies as well, Sharp said.

"We have already taken the step of notifying the credit card companies involved," he said. "We are suggesting they get in touch with their credit card companies and put a fraud alert on their records and keep a close eye on their credit records."

AT&T discovered the unauthorized electronic access within hours after it took place and shut down the site, which is operated by a vendor, immediately, he said.

The fact that a huge corporate entity such as AT&T was hacked is not unusual, said Brad Thomas, vice president of technology at Oklahoma City-based Perimeter Technology Center.

"My perspective is there isn't any company that is immune to this type of break-in," Thomas said. "Certainly you would expect the highest level of security would be put in place. But if someone wants the data bad enough ... the whole premise (of security) is to make the cost of getting to the data more than the data is worth.

"There is no such thing as fool-proof security."

Forensic teams and law enforcement are working to determine how the theft occurred and who was responsible, AT&T's Sharp said.

AT&T's online store for DSL equipment was the only company site infiltrated by the hackers, he said. Subscribers to DSL service were not affected.

Sharp said the company's online store selling telephones was not affected but was shut down also as a precaution.

Beth Givens, director of the Privacy Rights Clearinghouse, a California-based nonprofit, said her group has tallied more than 170 publicly disclosed security breaches nationwide of sensitive personal information so far this year.

A Texas law enacted last year mandates that companies disclose such security breaches to the public.