Zeus Botnet Eurograbber Steals $47 Million

Who Is Hacking U.S. Banks? 8 Facts

A criminal gang wielding a new version of Zeus malware that's designed for mobile devices has stolen an estimated 36 million euros, or $47 million, from more than 30,000 corporate and private banking customers.

That finding comes from a new report published by security vendors Versafe and Check Point Software Technologies. They've dubbed the related attack campaign as "Eurograbber," and notified banks and law enforcement agencies in the affected countries.

Attackers have configured the malware to target customers of 16 specific banks in Italy, as well as seven in Spain, six in Germany and three in the Netherlands. "To date, this exploit has only been detected in euro zone countries, but a variation of this attack could potentially affect banks in countries outside of the European Union as well," according to the report. Individual transfer amounts made by Eurograbber malware have ranged from 500 euros ($656) to 250,000 euros ($328,000).

The malware used by attackers is a customized version of the Zitmo Trojan spyware application. Zitmo is short for "Zeus in the mobile," and the malware is designed to defeat the two-factor authentication systems employed by some banks. To do that, a companion, smartphone version of the malware intercepts the one-time transaction authentication number (TAN) that banks send to a customer's mobile device, via SMS, which the customer must then enter into a banking website prompt to authorize a money transfer.

[ Here is a good question: Can Banks Prevent The Next Cyber Attack? ]

The Zitmo Trojan can infect a PC if a user clicks on a malicious link in a spam or phishing email, or on a link on a website that's been compromised by attackers. The malicious Trojan application then remains dormant until a user logs into a targeted financial firm's website. "The next time the bank customer logs in to their bank account, the Eurograbber Trojan intercepts their banking session and injects a JavaScript into the customer's banking page," according to the report. "This malicious JavaScript informs the customer of the 'security upgrade' and instructs them on how to proceed."

The security upgrade page requests that the user indicated which mobile operating system their smartphone uses -- Android, BlackBerry, iOS (iPhone), Symbian (Nokia) or other -- as well as their mobile phone number. This information is then relayed to a drop zone, which is a publicly writable folder on a Web server -- which attackers may have previously hijacked -- where they store information about every infected bank customer's PC, including account numbers, log-in credentials, and one-time passwords.

A bogus confirmation SMS is then sent to the user's smartphone. "The SMS directs the customer to complete the security upgrade by clicking on the attached link. Doing so downloads a file onto the customer's mobile device with the appropriate mobile version of the Eurograbber Trojan," according to the report.

From then on, anytime that PC is used to log onto the targeted financial website, automatic attacks may take place, with the malware on the PC initiating transfers, and the malware on the smartphone intercepting any TAN sent by the bank, and automatically approving the transaction, which transfers money to mule accounts. "Victims' bank accounts will have lost money without their knowledge," according to the report. "This entire process occurs every time the bank customer logs into his or her bank account."

News of the Eurograbber Zitmo attack campaign follows the recent discovery of a cybercrime campaign waged using the Gameover Zeus Trojan, which steals banking credentials using phony but real-looking emails. Millions of those emails have been circulating in recent weeks, and are being distributed via the Cutwail spamming botnet.