Attack Chain

1. Attacker gains initial local access to a Windows system, potentially through phishing, social engineering, or exploiting another vulnerability.
2. Attacker identifies the presence of Avast Antivirus or AVG Technologies Anti-Virus on the system.
3. Attacker leverages an unspecified vulnerability within Avast or AVG to execute code with elevated privileges.
4. The attacker crafts a malicious payload designed to exploit the vulnerability.
5. The payload interacts with vulnerable Avast/AVG processes, triggering the privilege escalation.
6. Attacker successfully escalates privileges, gaining SYSTEM or Administrator level access.
7. Attacker leverages escalated privileges to install malware, modify system configurations, or exfiltrate sensitive data.
8. Attacker maintains persistence on the compromised system using the newly acquired elevated privileges.

Impact

Successful exploitation of this vulnerability allows a local attacker to escalate their privileges to SYSTEM or Administrator, leading to complete system compromise. This can result in data theft, malware installation, and unauthorized access to sensitive information. While the exact number of potential victims is unknown, given the widespread use of Avast and AVG antivirus products, the impact could be significant.

Recommendation

• Monitor process creation events for suspicious activity involving Avast Antivirus and AVG Technologies Anti-Virus binaries using the provided Sigma rules.
• Investigate any unusual registry modifications or file system changes performed by Avast or AVG processes, looking for signs of exploitation based on the Sigma rules.
• Conduct regular security audits of systems running Avast and AVG antivirus products to identify and remediate any potential misconfigurations that could facilitate exploitation.