Hackers broke into an online store operated by US telco AT&T and stole the credit card details of 19,000 customers.
The unauthorised electronic access took place over the weekend and affected customes who purchased DSL equipment through the company's online Web store.
AT&T says it has notified the major credit card companies whose customer accounts were involved and that it is working with law enforcement to investigate the incident and pursue the perpetrators.
Priscilla Hill-Ardoin, chief privacy officer for AT&T says: "We deeply regret this incident and we intend to pay for credit monitoring services for customers whose accounts have been impacted. We will work closely with law enforcement to bring these data thieves to account."