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Safeguarding Android Users From Zero-Day Attacks

TAG is actively tracking more than 30 vendors providing exploits to government-backed entities, with different levels of sophistication.

 

The term "zero-day" refers to newly found security flaws that hackers can exploit to attack systems. It refers to the fact that the vendor or developer only recently discovered the fault, leaving them with "zero days" to repair it. A zero-day attack is when a zero-day exploit is used to harm or steal data from a system that has been exposed to a vulnerability.

Google's Threat Analysis Group (TAG) is always on the lookout for zero-day exploits. In 2021, it revealed nine zero-day exploits impacting Chrome, Android, Apple, and Microsoft, resulting in updates to safeguard consumers. Google believes that these attacks were bundled by a single commercial monitoring firm called Cytrox.

Cytrox is a North Macedonian firm with offices in Israel and Hungary that was exposed in late 2021 as the creator and maintainer of the spyware "Predator". 

According to new Google research, Cytrox offers new exploits to government-backed actors, who subsequently deploy them in three separate attack campaigns. Egypt, Armenia, Greece, Madagascar, Côte d'Ivoire, Serbia, Spain, and Indonesia are among the actors who purchased Cytrox services. 

The hackers take advantage of the time differential between when some significant problems were patched but not identified as security issues and when these fixes were fully propagated across the Android ecosystem, using 0-day exploits alongside n-day exploits. 

These findings highlight the extent to which commercial surveillance vendors have proliferated capabilities that were previously solely available to governments with the technical know-how to build and deploy exploits. TAG is actively tracking more than 30 vendors providing exploits or surveillance capabilities to government-backed entities, with different levels of sophistication and public exposure.

The three initiatives were all emailed to targeted Android users with one-time URLs that looked like URL shortener services. The campaign was small - researchers estimate that the number of users targeted in each case was in the tens of thousands. When the link was clicked, the target was sent to an attacker-controlled domain that provided the bugs before redirecting the browser to a legitimate website. The user was forwarded to a valid website if the link was not active. These ads are believed to be transmitted by ALIEN, a simple Android malware capable of loading PREDATOR, an Android implant first reported by CitizenLab in December 2021. 

  • Campaign 1 – Chrome redirection to SBrowser (CVE-2021-38000): In August 2021, the first campaign was discovered using Chrome on a Samsung Galaxy S21, and the webserver immediately responded with an HTTP redirect (302) pointing to the following intended URL. This URL took use of a logic issue in Chrome to force the Samsung Browser to load another URL without user intervention or warnings. 
  • Campaign 2 – Chrome sandbox escape: TAG discovered a campaign in September 2021, in which the exploit chain was sent to a fully updated Samsung Galaxy S10 running Chrome. The exploit that was utilized to get out of the Chrome Sandbox was retrieved, but not the original RCE exploit. The libchrome-embedded sandbox escape was loaded directly as an ELF binary. Libmojo bridge is also custom. The exploit was found to have two separate vulnerabilities in Chrome that are given below: 
  1. CVE-2021-37973: In the handling of Portals API and Fenced subframes, there is a use-after-free vulnerability. 
  2. CVE-2021-37976: A memory instrumentation. mojom. Coordinator information leak allows privileged programs to obtain Global Memory Dumps. These dumps contain sensitive data (addresses) that can be utilized to circumvent ASLR. After escaping the sandbox, the vulnerability downloaded another exploit to raise privileges and install the implant in /data/data/com.android.chrome/p.so. 
  • Campaign 3 – Android 0-day exploit chain in its entirety (CVE-2021-38003, CVE-2021-1048): A full chain exploits on an up-to-date Samsung phone running the newest version of Chrome in October 2021. Two zero-day exploits were included in the chain: CVE-2021-38003, a JSON renderer 0-day vulnerability. The whole value is leaked, allowing the attacker to totally exploit the renderer. The sandbox escape relied on a Linux kernel fault in the epoll() system call. The attacker can use this system call to escape the BPF sandbox and compromise the system by injecting code into privileged processes. 
Google hasn't been able to locate a copy of the exploit and will continue to keep the community informed as they learn more about these campaigns. To combat these issues, a robust, comprehensive approach will be required, involving collaboration between threat intelligence teams, network defenders, university researchers, and technology platforms.
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