Verizon Wireless said yesterday that computer programming flaws in its online billing system could have allowed customers to view account information belonging to other customers, possibly exposing limited personal information about millions of people.
A spokesman for the Bedminster, N.J., company, a joint venture between Verizon Communications Inc. and Vodafone Group PLC, declined to say how many of the company's 45 million subscriber accounts were at risk. Verizon Wireless said the problem appeared to be limited to accounts for customers in the eastern United States who had signed up for its "My Account" feature.
There was no indication that anyone took advantage of the flaws or that any customer financial information, such as Social Security or credit card account numbers, was disclosed, Verizon Wireless spokesman Tom Pica said. The flaws also did not allow access to phone numbers associated with customers' incoming and outgoing calls, and "no customer data could be manipulated and changed in any way," Pica said.
Verizon Wireless said it had corrected the problem as of 2 a.m. yesterday. Pica said the company was still assessing whether it would notify customers about the situation.
The "My Account" feature has been available on the Verizon Wireless Web site for five years. Pica said the company does not yet know how long the flawed coding had been in place.
Pica confirmed the Web site flaw could have allowed a user to view another subscriber's balance of remaining airtime minutes and the number of minutes that customer had used in the current billing cycle. Two other flaws could have exposed data about a customer's general location -- city and state -- and the make and model of phone the customer uses, Pica said.
The flaw that exposed account information was reported to Verizon Wireless by Jonathan Zdziarski, a software developer from Milledgeville, Ga., who said he discovered it while writing a computer program that would automatically query his account online and report the number of minutes he had used from his wireless plan.
Zdziarski found that by simply entering another subscriber's wireless phone number on a particular portion of the site, he could pull up some information about that person's account.
Pica said the flaws did not expose customer account balances or latest payment information. But Zdziarski provided washingtonpost.com with a screenshot showing that the vulnerabilities exposed account balances and the date of the most recent payment, a claim that Pica said the company could not confirm.
After Zdziarski's alert, Verizon Wireless technicians reviewed other portions of the company's billing system and fixed one flaw but disabled the feature that allowed viewing of customer location until technicians could figure out a way to secure it, according to Pica.
Zdziarski said he later conducted other tests and found that the problem he discovered also could be exploited to transfer one customer's account to another handset, a technique known as "cloning."
The user of a cloned phone can intercept all of the victim's incoming wireless calls and make calls that would be billed to the victim's account. Zdziarski said he was prevented from fully testing whether the flaw could be used to clone Verizon Wireless phones because the service that allows customers to map existing phone numbers to new handsets appeared to be offline when he reported the flaw.
"This was a very easy hack to do," Zdziarski said. "I'm sure if I've discovered it, then certainly your typical 'script kiddie' could figure it out."
Pica said company technicians were unable to reproduce the phone-cloning scenario described by Zdziarski.
One of Verizon Wireless's competitors, Bellevue, Wash.-based T-Mobile International, disclosed in January that a security hole in its Web site exposed data on at least 400 customers, including a Secret Service agent. This year, a group of hackers used other flaws in T-Mobile's site to break into the phones of dozens of celebrities in an incident that exposed racy photographs and personal notes and contacts for hotel heiress and socialite Paris Hilton.
Krebs is a reporter for washingtonpost.com.