A malicious extension for Chromium-based web browsers has been observed to be distributed via a long-standing Windows information stealer called ViperSoftX.
Czech-based cybersecurity company dubbed the rogue browser add-on VenomSoftX owing to its standalone features enabling it to access website visits, steal credentials and clipboard data, and even swap cryptocurrency addresses via an adversary-in-the-middle (AiTM) attack.
“This multi-stage stealer exhibits interesting hiding capabilities, concealed as small PowerShell scripts on a single line in the middle of otherwise innocent-looking large log files, among others,” Avast researcher Jan Rubín said in a technical write-up.
“ViperSoftX focuses on stealing cryptocurrencies, clipboard swapping, fingerprinting the infected machine, downloading and executing arbitrary additional payloads, or executing commands.”
The distribution vector used to propagate ViperSoftX is typically achieved through cracked software for Adobe Illustrator and Microsoft Office that are hosted on file-sharing sites.
The downloaded executable file comes with a clean version of cracked software and additional files that set up persistence on the host and harbor the ViperSoftX PowerShell script.
Newer malware variants can also load the VenomSoftX add-on, retrieved from a remote server to Chromium-based browsers such as Google Chrome, Microsoft Edge, Opera, Brave, and Vivaldi.
This is achieved by searching for LNK files for the browser applications and modifying the shortcuts with a “–load-extension” command line switch that points to the path where the unpacked extension is stored.
The extension disguises itself as well-known and common browser extensions such as Google Sheets. In reality, VenomSoftX is yet another information stealer deployed onto the unsuspecting victim with full access permissions to every website the user visits from the infected browser.
It’s worth noting that the –load-extension tactic has also been put to use by another browser-based information stealer referred to as ChromeLoader (aka Choziosi Loader or ChromeBack).
VenomSoftX, like ViperSoftX, is also orchestrated to steal cryptocurrencies from its victims. But unlike the latter, which functions as a clipper to reroute fund transfers to an attacker-controlled wallet, VenomSoftX tampers with API requests to crypto exchanges to drain the digital assets.
Services targeted by the extension include Blockchain.com, Binance, Coinbase, Gate.io, and Kucoin.
The development marks a new level of escalation to traditional clipboard swapping while not raising any immediate suspicion as the wallet address is replaced at a much more fundamental level.