Google published a six-part report today detailing a sophisticated hacking operation that the company detected in early 2020 and which targeted owners of both Android and Windows devices.
The attacks were carried out via two exploit servers delivering different exploit chains via watering hole attacks, Google said.
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"One server targeted Windows users, the other targeted Android," Project Zero, one of Google's security teams, said in the first of six blog posts.
Google said that both exploit servers used Google Chrome vulnerabilities to gain an initial foothold on victim devices. Once an initial entry point was established in the user's browsers, attackers deployed an OS-level exploit to gain more control of the victim's devices.
The exploit chains included a combination of both zero-day and n-day vulnerabilities, where zero-day refers to bugs unknown to the software makers, and n-day refers to bugs that have been patched but are still being exploited in the wild.
All in all, Google said the exploit servers contained:
The four zero-days, all of which were patched in the spring of 2020, were as follows:
Google said that while they did not find any evidence of Android zero-day exploits hosted on the exploit servers, its security researchers believe that the threat actor most likely had access to Android zero-days as well, but most likely weren't hosting them on the servers when its researchers discovered it.
Overall, Google described the exploit chains as "designed for efficiency & flexibility through their modularity."
"They are well-engineered, complex code with a variety of novel exploitation methods, mature logging, sophisticated and calculated post-exploitation techniques, and high volumes of anti-analysis and targeting checks," Google said.
"We believe that teams of experts have designed and developed these exploit chains," but Google stopped short of providing any other details about the attackers or the type of victims they targeted.
Together with its introductory blog post, Google has also published reports detailing a Chrome "infinity bug" used in the attacks, the Chrome exploit chains, the Android exploit chains, post-exploitation steps on Android devices, and the Windows exploit chains.
The provided details should allow other security vendors to identify attacks on their customers and track down victims and other similar attacks carried out by the same threat actor.
Article title updated shortly after publication, changing the term "massive" to "sophisticated" as there is no information on the scale of this operation to support the initial wording.