Time Warner Cable Inc said on Wednesday up to 320,000 customers may have had their email passwords stolen.
The company said email and password details were likely gathered either through malware downloaded during phishing attacks or indirectly through data breaches of other companies that stored Time Warner Cable's customer information, including email addresses.
The company said it has not yet determined how the information was obtained, but there were no indications that Time Warner Cable's systems were breached.
Time Warner Cable spokesman said it was recently notified by the Federal Bureau of Investigation that some customers' email addresses including account passwords "may have been compromised."
The company said it is sending emails and direct mail correspondence to encourage customers to update their email passwords as a precaution.