On Thursday 4th of January, Bojan Zdrnja, a Croatian security researcher, shared his discovery, wherein a malicious Chrome extension exploited the Chrome sync as a way to connect with a remote command and control (C&C) server and to exfiltrate the details from compromised browsers during the latest incident reaction.
In addition, Zdrnja added that the attackers had gotten access to a victim's device during the incident he investigated, however, because the data they tried to steal was inside the worker's portal, therefore they downloaded Chrome extension on the user’s system and loaded it in Developer's Mode. It included malicious code that abused Chrome's synchronized functionality to allow attackers to monitor the infected browser, which was used as a security add-on by security company Forcepoint.
Zdrnja claimed that the purpose of this unique attack was to use the extension to "manipulate data in an internal web application that the victim had access to."
"While they also wanted to extend their access, they actually limited activities on this workstation to those related to web applications, which explains why they dropped only the malicious Chrome extension, and not any other binaries," Zdrnja stated in a report.
"In order to set, read or delete these keys, all the attacker has to do is log in with the same account to Google, in another Chrome browser (and this can be a throwaway account), and they can communicate with the Chrome browser in the victim's network by abusing Google's infrastructure," he added, wherein data stored in the key field could be anything. For instance, data obtained from the infected browser may be malicious extensions or commands the attacker desires to run the extension at an infected workstation (for example, usernames, passwords, cryptographic keys, or more).
Although the stolen content or corresponding commands are transmitted via Chrome's infrastructure, no process can be inspected or blocked in the majority of corporate networks, which are normally authorized to run and transfer data unimpeded by the Chrome browser.
The researcher recommended businesses to use Chrome company and community decision assistance to block and monitor the plugins that could be installed on a browser, prohibiting rogue extensions, such as the one he investigated, from being installed.