Telecommunications giant AT&T disclosed on June 13 that three employees of one of its vendors used their privileged access to hack a server containing sensitive customer data, including Social Security Numbers, birth dates and cellular phone numbers. Thus far, AT&T hasn’t revealed how many are affected by this breach, and for the moment it appears that the hackers gained unauthorized access for the purposes of unlocking older generation AT&T phones for use on other carrier networks. The breaches happened in April, but AT&T is only just now notifying affected customers.

What this means for you:

Unlike previous data breaches, the exposed customer data hasn’t appeared for sale (yet!) on the internet black market, but AT&T is offerring a free year of credit monitoring as a mea culpa to its affected customers. If you were affected by this breach, you should have already received a notice from AT&T of the potential exposure. This latest breach demonstrates an important point about security: no matter how much you invest in protecting your perimeter, serious threats may already be behind your “firewall”. As an individual, there is very little you can do to help AT&T be more secure, but you can take your credit history and activity seriously, and always keep your eyes peeled for unusual activity on any online account, regardless of whether they are financial services or not.