In February, security experts discovered an attack using a zero-day vulnerability in the Microsoft Common Log File System (CLFS).
A cybercriminal group used an exploit developed for different versions and builds of Windows OS, including Windows 11, and attempted to deploy the Nokoyawa ransomware.
Microsoft assigned CVE-2023-28252 to this vulnerability and patched it today as part of Patch Tuesday.
The threat actor also attempted to execute similar elevation of privilege exploits in attacks on different small and medium-sized businesses in the Middle East and North America, and previously in Asia.
While most of the vulnerabilities discovered by researchers at Kaspersky are used by APTs, this one turned out to be exploited for cybercrime purposes by a sophisticated group that carries out ransomware attacks.
This group stands out by the usage of similar but unique Common Log File System (CLFS) exploits. Kaspersky has seen at least five different exploits of this kind.
They were used in attacks on retail and wholesale, energy, manufacturing, healthcare, software development, and other industries.
Microsoft assigned CVE-2023-28252 to the discovered zero-day. This is the Common Log File System elevation of privilege vulnerability, which gets triggered by the manipulation of file formats used by this subsystem.
Researchers uncovered the vulnerability in February as a result of additional checks into a number of attempts to execute similar elevation of privilege exploits on Microsoft Windows servers belonging to different small and medium-sized businesses in the Middle Eastern and North American regions.
CVE-2023-28252 was first spotted in an attack where cybercriminals attempted to deploy a newer version of Nokoyawa ransomware.
Older variants of this ransomware were just “rebranded” variants of JSWorm ransomware, but in the aforementioned attack, the Nokoyawa variant was quite distinct from JSWorm in terms of a codebase.
The exploit used in the attack was developed to support different versions and builds of Windows OS, including Windows 11.
Attackers used the CVE-2023-28252 vulnerability to elevate privileges and steal credentials from the Security Account Manager (SAM) database.
“Cybercrime groups are becoming increasingly more sophisticated using zero-day exploits in their attacks. Previously, it was primarily a tool of Advanced Persistent Threat actors (APTs), but now cybercriminals have the resources to acquire zero-days and routinely use them in attacks,” said Boris Larin, Lead Security Researcher with the Global Research and Analysis Team (GReAT).
There are also exploit developers willing to help them and develop exploit after exploit. It’s very important for businesses to download the latest patch from Microsoft as soon as possible, and use other methods of protection, such as EDR solutions,” Larin added.
To protect your organization from attacks that exploit the aforementioned vulnerability, experts recommend:
- Update your Microsoft Windows as soon as possible, and do so regularly
- Use a reliable endpoint security solution such as Endpoint Security for Business that is powered by exploit prevention, behavior detection, and a remediation engine that is able to roll back malicious actions.
- Install anti-APT and EDR solutions, enabling capabilities for threat discovery and detection, investigation, and timely remediation of incidents. Provide your SOC team with access to the latest threat intelligence and regularly upskill them with professional training.
