Time Warner Cable said on Wednesday that up to 320,000 customers have had their accounts compromised.
The ISP first learned of the problem after the FBI contacted them about email addresses and passwords that might have been compromised.
Eric Mangan, public relations director for Time Warner Cable, told Salted Hash that impacted customers would be contacted via email and direct mail. Those contacted will be encouraged to change their passwords.
"Approximately 320,000 customers across our markets could be impacted by this situation. To protect the security of these customers, we are sending emails and direct mail correspondence to encourage them to update their email passwords as a precaution," Mangan said.
"We have not yet determined how the information was obtained, but there are no indications that TWC’s systems were breached.
The emails and passwords were likely previously stolen either through malware downloaded during phishing attacks or indirectly through data breaches of other companies that stored TWC customer information, including email addresses.
For those customers whose account information was stolen, we are contacting them individually to make them aware and to help them reset their passwords."
The notion of a targeted Time Warner Cable list online isn't far fetched.
Criminals will sometimes take bulk lists of compromised account data (such as email addresses and passwords), and compile them into a single list sorted by ISP or location.
These lists are then sold and traded to anyone who requests them.
Last November, Salted Hash broke the story of one such list. That list focused on Comcast customers, and it was being offered up for $300 for 100,000 accounts, or $1,000 for the entire list.
The list was somewhat outdated, but Comcast still needed to reset 200,000 passwords because of it.