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Amit Klein, CTO of Trusteer, said “In addition to stealing bank account data, these Ice IX configurations are capturing information on telephone accounts belonging to the victims. This allows attackers to divert calls from the bank intended for their customer to attacker controlled phone numbers. I 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 (discussed in a previous Trusteer blog) that approve the transactions.”

In one attack captured by Trusteer researchers, at login the malware steals the victim’s user id and password, memorable information/secret question answer, date of birth and account balance.

Next, the victim is asked to update their phone numbers of record (home, mobile and work) and select the name of their service provider from a drop-down list. In this particular attack, the three most popular phone service providers in the UK are presented: British Telecommunications, TalkTalk and Sky. Here’s an example of the web injection the user sees in their browser:

To enable the attacker to modify the victim’s phone service settings, the victim is then asked by the malware to submit their telephone account number. This is very private data typically only known to the phone subscriber and the phone company. 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".

Amit Klein, CTO of Trusteer said, “As Trusteer discussed in a recent blog, fraudsters are increasingly turning to these post-transaction attack methods to hide fraudulent activity from the victim and block email and phone communication from the bank. This allows attackers to circumvent security mechanisms that look for anomalies once transactions have already been executed by the user.”

Deterministic detection security mechanisms like Trusteer Rapport, which search for specific malware Crime Logic footprints before transactions are submitted and allow the online banking application to stop fraud by changing business flows (block money transfers, decline add payee, limit amounts, etc.), are not vulnerable to post transaction attacks.

Thanks to Tanya Shafir from Trusteer’s analysis team for providing the intelligence for this alert.