This Open-Source Tool Protects Your MBR from Ransomware

Cisco Systems’ Talos cybersecurity team has released an open-source available freely to protect the master boot record of a computer from the menace of malware including ransomware. 

The Master Boot Record (MBR) is a common target for malware, as the first sector on any hard drive that stores the bootloader required for booting any computer’s operating system. Malware authors have predictably targeted the MBR records on computers, in an attempt to clamp down the entire computer rather than focusing on files on the hard drive.

A malware program that is efficient in what it does, modifies the MBR in its attempt to infect computers, with programs typically known as a rootkit or bootkit. Bootkit , or a boot-specific malware installs ransomware and other malicious software into the Windows kernel of a target’s computer, making it near impossible to detect. If successful, the bootkit triggers a compromise of the targeted victim’s entire computer.

Suffice to say, it is important that the MBR is protected, while any channels to tweak or modify the MBR from unauthorized programs ought to be plugged.

The Talos team from Cisco has devised a free tool called the MBRFilter, which uses a simple yet effective method to outmaneuver rogue malware. Basically, the MBRFilter acts as a signed system driver that renders the MBR into a read-only record. This, effectively, kills any chances of malware or software modifying the MBR for any nefarious purposes.

In a blog post, Talos explained:

MBRFilter is a simple disk filter based on Microsoft’s diskperf and classpnp example drivers. It can be used to prevent malware from writing to Sector 0 on all disk devices connected to a system.

When installed, the system will be required to boot into Safe Mode, to leave Sector 0 of the disk, which contains the MBR, become accessible for modification by the tool.

The Talos team demonstrated the use of the tool on a virtual machine infected by the Petya ransomware, rendering the notable menace obsolete following MBRFilter’s installation.

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