Yahoo hack: It's not just Verizon; AT&T customers should be worried too.

The massive hack that Yahoo disclosed last week is a headache for Verizon, the telecom giant set to take ownership of the company early next year.

Rival AT&T should be nervous too...

That's because many AT&T customers get the option to use a Yahoo Mail account to manage services like home broadband, wireless and pay-television services.

It's the outgrowth of a partnership from 15 years ago between Yahoo and AT&T (then called SBC Communications), bringing AT&T broadband customers to Yahoo's search engine and media services, including Yahoo Mail. At the time, critics hailed the deal as a landmark partnership that would better combat the growing power of AOL and Microsoft's MSN portal.

Today, AOL is part of Verizon, Microsoft's MSN is no more and AT&T likely isn't feeling so great about the deal.

Yahoo said Thursday that the hack compromised at least half a billion accounts containing user names, email addresses and passwords. That makes it the biggest attack ever. US Senator Mark Warner has asked the Securities and Exchange Commission to investigate the matter.                                    
The hack puts AT&T in an uncomfortable position. The company is still waiting for data from Yahoo on the specific customers who may have been affected, according to a person familiar with their dealings.

"We began investigating immediately and requested information from Yahoo necessary to determine which email accounts may have been compromised," the company said in a statement. "In the meantime, we are in the process of notifying potentially affected customers."

Chances are, a significant number of AT&T customers are affected.

AT&T was in the middle of breaking up with Yahoo before the attack, having announced in May that it would instead tap Synacor to handle its internet and mobile portal business.

 

The loss of the deal, worth an estimated $100 million a year, came at a time when chatter had heated up over potential suitors for Yahoo. AT&T was among the rumored bidders, but Verizon snagged the internet pioneer with a $4.8 billion offer.

For now, AT&T is offering little advice to its customers beyond the standard line: regularly change your passwords.

That, along with these other tips, is advice everyone should heed.