A major credit card processor, Heartland Payment Systems, revealed this week that hackers have compromised its computer network and gained access to the system it uses to process 100 million payment card transactions per month for 175,000 merchants. That number, if verified, would make this one of the largest data breaches on record and could even surpass TJ Maxx’s embarrassing mishap in 2007.

Heartland’s problems began late last year when the company was alerted by Visa and MasterCard of suspicious activity surrounding processed card transactions. The company then began an investigation, which lead to the data-stealing malware planted by thieves, apparently around November. No personally identifiable information has been stolen but, according to Heartland, but the magnetic information stored on the back of credit cards was indeed compromised and could be used to duplicate a card.

The company said it immediately took a number of steps to secure its systems and created a website – www.2008breach.com – to provide information about the incident. In addition, Heartland assured cardholders that they would not be held responsible for any unauthorized, fraudulent charges made by third parties.