Security researchers observed the RobbinHood ransomware family abusing a vulnerable driver to delete security products before initiating its encryption routine.

In its analysis of two RobbinHood ransomware attacks, Sophos spotted the threat abusing CVE-2018-19320 in a signed Gigabyte driver to circumvent security products on an infected machine. It began this functionality by running its STEEL.exe application. This application was responsible for installing both the signed Gigabyte driver and an unsigned malicious kernel driver capable of killing processes associated with security products.

Rather than purchase a digital certificate for its own driver, the ransomware exploited the privilege escalation vulnerability found in the Gigabyte driver to temporarily disable driver signature enforcement in Windows. This technique allowed the ransomware to load its unsigned driver and use it to kill security processes listed in a PLIST.TXT file. Having disabled those processes, the threat then initiated its encryption routine.

According to Sophos, Gigabyte discontinued using its vulnerable driver some time ago. However, as of this post, the driver was still available, and Verisign had not revoked the certificate used for the driver.

The Ongoing Evasion Efforts of Ransomware Families

RobbinHood ransomware isn’t the first crypto-malware family to try to evade detection by security products. In September 2019, Bleeping Computer spotted an update in the Nemty ransomware family that allowed new samples to kill security processes and services.

In November 2019, Bleeping Computer discovered a sample of Clop ransomware attempting to disable Windows Defender as well as remove both Microsoft Security Essentials and Malwarebytes’ standalone anti-ransomware program. About a month later, Sophos uncovered a sample of Snatch ransomware booting infected computers into Safe Mode in order to bypass protection.

How to Defend Against RobbinHood Ransomware

Security professionals can help their organizations defend against a RobbinHood ransomware attack by developing an incident response plan and practicing it on a regular basis. This will help the organization respond more quickly in the event of a ransomware infection. Companies should also consider conducting cyber resiliency workshops to evaluate the strength of their defenses, both technological and human-based, in the face of a ransomware attack.

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