'Self-deleting' Mexican ATM malware let sneaky miscreants slurp cash

Software nasty can be planted, operate and wipe itself all without detection

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Security researchers have lifted the lid on a new ATM malware strain, dubbed GreenDispenser, which gives crooks the ability to walk up to a compromised machine and drain its cash.

When installed, GreenDispenser displays an “out of service” message on the ATM – but attackers who enter the correct pin codes can then drain the ATM’s cash before deleting the malware, leaving little trace of how the ATM was robbed.

Proofpoint has witnessed ongoing attacks based on the malware taking place in Mexico. It warns there's little to stop the same techniques from being abused in similar scams in other countries across the world.

The attack has striking similarities from the Ploutus malware scam that surfaced last year and was also linked to theft from ATMs in Mexico as well as another recent strain of ATM malware, dubbed Tyupkin.

Tyupkin first surfaced in Mexico but spread to part of Asia and Russia.

Kevin Epstein, vice president of Threat Operations for Proofpoint, told El Reg that GreenDispenser was a distinct, and in some ways more advanced, threat to predecessor such as Ploutus and Tyupkin.

GreenDispenser has the ability to target ATM hardware from multiple vendors using the XFS middleware standard, which is widely adopted by various ATM vendors.

Initial malware installation of GreenDispenser likely requires physical access to the ATM, raising questions of compromised physical security or corrupt insiders at banks. Once installed, GreenDispenser is similar in functionality to the Tyupkin (AKA Padpin) malware but does exhibit some unique functionality, such as date-limited operation and a form of two-factor authentication.

The malware strains Proofpoint inspected were coded to run only if the year was 2015 and the month was earlier than September, suggesting that GreenDispenser was employed in a limited operation and designed to deactivate itself to avoid detection. GreenDispenser bundles a batch script that uses sdelete to perform a deep delete to remove itself from an ATM.

Proofpoint suspects that cybercrook bosses have a mobile phone application that acts a form of "two-factor authentication" for cash mules involved in the scam. The functionality allows the gangmasters behind the scam to control who can cash out compromised machines, as explained in a blog post by Proofpoint here (extract below).

GreenDispenser employs authentication using a static hardcoded PIN, followed by a second layer of authentication using a dynamic PIN, which is unique for each run of the malware. The attacker derives this second PIN from a QR code displayed on the screen of the infected ATM. We suspect that the attacker has an application that can run on a mobile phone with functionality to scan the barcode and derive the second PIN – a two-factor authentication of sorts.

ATM malware strains such as GreenDispenser, Tyupkin and Ploutus each allow cybercriminals to attack financial institutions directly, without the extra steps required to capture credit and debit card information from consumers, potentially making attacks less traceable in the process. ®

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