Cisco’s Talos research team has open sourced MBRFilter, a tool that aims to prevent a system’s Master Boot Record (MBR) getting overwritten by malware.

The latest malware families that use this tactic are HDDCryptor (aka Mamba) and Petya, two pieces of ransomware that not only encrypt victims’ files, but also effectively lock them out of their computer by overwriting the MBR.