Visa Issues Alert for 'Baka' JavaScript Skimmer

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Aug 17, 2014
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A JavaScript skimmer identified earlier this year uses dynamic loading to avoid detection by static malware scanners, Visa warns.

Referred to as Baka, the e-commerce skimmer was first discovered in February 2020, but has already impacted several merchant websites across numerous global regions.

The skimmer is basic, containing the expected components and functionality of such a kit, namely an administration panel, an exfiltration gateway, and a skimming script generator, but has an advanced design, suggesting that it is the work of a skilled developer, Visa notes in a security alert (PDF).

Baka features a unique loader, loads dynamically, and obfuscates the malicious code with unique encryption parameters for each of its victims.
To further avoid detection and analysis, the skimmer removes itself from memory when detecting attempts for dynamic analysis using Developer Tools, as well as when the targeted data has been successfully exfiltrated, Visa Payment Fraud Disruption (PFD) says.

“The Baka loader works by dynamically adding a script tag to the current page. The new script tag loads a remote JavaScript file, the URL of which is stored encrypted in the loader script. The attacker can change the URL for each victim,” Visa explains.