A malicious browser extension with 350 variants is masquerading as a Google Translate add-on as part of an adware campaign targeting Russian users of Google Chrome, Opera, and Mozilla Firefox browsers.

Mobile security firm Zimperium dubbed the malware family ABCsoup, stating the "extensions are installed onto a victim's machine via a Windows-based executable, bypassing most endpoint security solutions, along with the security controls found in the official extension stores."

The rogue browser add-ons come with the same extension ID as that of Google Translate — "aapbdbdomjkkjkaonfhkkikfgjllcleb" — in an attempt to trick users into believing that they have installed a legitimate extension.

The extensions are not available on the official browser web stores themselves. Rather they are delivered through different Windows executables that install the add-on on the victim's web browser.

In the event the targeted user already has the Google Translate extension installed, it replaces the original version with the malicious variant owing to their higher version numbers (30.2.5 vs. 2.0.10).

"Furthermore, when this extension is installed, Chrome Web Store assumes that it is Google Translate and not the malicious extension since the Web Store only checks for extension IDs," Zimperium researcher Nipun Gupta said.

All the observed variants of the extension are geared towards serving pop-ups, harvesting personal information to deliver target-specific ads, fingerprinting searches, and injecting malicious JavaScript that can further act as a spyware to capture keystrokes and monitor web browser activity.

The main function of ABCsoup entails checking for Russian social networking services like Odnoklassniki and VK among the current websites opened in the browser, and if so, gather the users' first and last names, dates of birth, and gender, and transmit the data to a remote server.

Not only does the malware use this information to serve personalized ads, the extension also comes with capabilities to inject custom JavaScript code based on the websites opened. This includes YouTube, Facebook, ASKfm, Mail.ru, Yandex, Rambler, Avito, Brainly's Znanija, Kismia, and rollApp, suggesting a heavy Russia focus.

Zimperium attributed the campaign to a "well-organized group" of Eastern European and Russian origin, with the extensions designed to target Russian users given the wide variety of local domains targeted.

"This malware is purposefully designed to target all kinds of users and serves its purpose of retrieving user information," Gupta said. "The injected scripts can be easily used to serve more malicious behavior into the browser session, such as keystroke mapping and data exfiltration."