US mobile phone carrier AT&T is notifying millions of wireless customers that their customer proprietary network information (CPNI) was compromised in a data breach at a third-party vendor.
One of the largest carriers in the US, AT&T has roughly 200 million wireless customers, but only a small percentage of the total has been impacted by the incident.
“We recently determined that an unauthorized person breached a vendor’s system and gained access to your ‘customer proprietary network information’ (CPNI),” the company told impacted customers in an email notification, copies of which were shared by users on AT&T’s community forums.
“In our industry, CPNI is information related to the telecommunications services you purchase from us, such as the number of lines on your account or the wireless plan to which you are subscribed,” AT&T continued.
According to the company, however, no personal or financial information such as Social Security numbers or credit card data was impacted in the data breach.
The notification emails also informed customers that the issue was resolved and that authorities were informed of the incident.
“Our report to law enforcement does not contain specific information about your account, only that the unauthorized access occurred,” the company said.
Some users reported they were informed that the exposed data included names, email addresses, wireless phone numbers, and wireless account numbers, along with “the number of lines on the account and basic device and installment agreement information”.
In some cases, information such as monthly payment amount, past due amount, rate plan name, and monthly charges and/or minutes used was also exposed.
AT&T has not named the impacted vendor, but told the media that it provides marketing services. The company said roughly 9 million customers were impacted by the incident.
SecurityWeek has emailed AT&T for additional information on the data breach and will update this article as soon as a reply arrives.
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