Attackers Divert Bank Phone Calls to Cover Tracks

A new version of a sneaky piece of banking malware has been armed with a new feature to help attackers cover their tracks.

According to Trusteer, certain new configurations of Ice IX – a modified variant of the Zeus platform – are capturing telephone account information belonging to their victims. The goal is to enable the attackers to divert calls from banks that are intended for the customer to telephones controlled by the attacker.

“We believe the fraudsters are executing fraudulent transactions using the stolen credentials and redirecting the bank’s post-transaction verification phone calls to professional criminal caller services…that approve the transactions,” noted Amit Klein, CTO of Trusteer.

In one attack observed by researchers at Trusteer, the malware stole the victim’s user ID and password as well as their secret question answer, date of birth and account balance at login. In the second phase of the attack, the victim is asked to update their home, mobile and work telephone information and select the name of their service provider from a drop-down list featuring three popular UK providers: British Telecommunications, TalkTalk and Sky. Next, the victim is asked to submit their telephone account number.

“This is very private data typically only known to the phone subscriber and the phone company,” explained Klein. “It is used by the phone company to verify the identity of the subscriber and authorize sensitive account modifications such as call forwarding. The fraudsters justify this request by stating this information is required as a part of verification process caused by "a malfunction of the bank’s anti-fraud system with its landline phone service provider".”

The end result is that attackers can circumvent attempts by the bank to alert customers via phone of malicious activity. Such activities are no longer rare, noted Liam O Murchu, manager of operations for Symantec Security Response.

“Common post-theft activities we’ve observed include acting as a man-in-the-browser, whereby the malware prevents the end user from seeing fraudulent transactions on the bank’s website, ensuring the victims do not suspect any nefarious activity has occurred behind the scenes,” he said. “We’ve been seeing this tactic for a few years. Another example of such activity is malware that modifies the banking webpage displayed in the browser in a manner to prevent certain actions, such as printing a statement, logging off, etc. One such threat is W32.Qakbot.”

Ice IX is actually one of the first spin offs of Zeus to appear last year after the Zeus source code was leaked. The malware is not particularly prevalent at this point, especially next to the native Zeus code’s binaries, Vikram Thakur, principal security response manager at Symantec, told Dark Reading.

“We think the reason for this is because most people who are feeding off the Zeus source code aren’t necessarily developers and simply compile and use what they already have in their possession,” he said.

“Zeus is by far the most prevalent banking malware in the wild today,” Murchu added. “That being said, there are other sophisticated pieces of malware in the wild that use rootkits to cover their tracks and are involved in siphoning information off one’s computer without specifically targeting banking information.”