Group points to VOIP flaw in DSL home gateway

A flaw in a DSL home gateway could lead broadband users to divulge personal information over the phone to someone they erroneously believe is calling from their bank, according to a group of self-styled ethical hackers.

BT's Home Hub, issued to the company's U.K. broadband subscribers, has an authentication vulnerability that enables a Web site rigged with malicious JavaScript to initiate a phone call, according to the group, GNUCitizen.

"We can tell your Home Hub to start a VOIP connection with any telephone number on the planet," said Adrian Pastor in a video posted on the group's blog.

Those at risk are subscribers using BT Home Hub firmware version 6.2.6.B with BT's Broadband Talk VOIP service, Pastor said.

For a successful attack, a person has to be lured to a Web site hosting the malicious JavaScript. That could be accomplished by sending a fraudulent e-mail from the person's bank saying he should to click on the link, which launches the JavaScript, said researcher Petko Petkov, in the same video.

Clicking on the link starts the attack. The victim's phone rings, and the gateway then initiates a call to another phone number. The victim thinks he is receiving a call, but actually he is making a VOIP call from his home gateway.

There are at least a couple scenarios for how a hacker could capitalize on the flaw. If the broadband subscriber thinks he is receiving a call from his bank, the person on the other end could persuade the victim to give up his bank account numbers.

The attacker could also make the victim's computer call a premium-rate phone line controlled by the hacker, who would receive a fee every time the number is called.

Pastor posted proof-of-concept code for the attack on a Web page. However, it wasn't immediately apparent if it works, as visitors would have to use BT's Home Hub with the correct software version.

BT said it's unlikely that the attack scenarios described by Pastor and Petkov could affect its customers, and no customers have reported such an attack, a BT spokesman said.

The IDG News Service is a Network World affiliate.