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Mebromi BIOS Rootkit

Mebromi is a trojan that contains several rootkits and has been sold on underground markets since 2011. It was the first to be discovered in the wild that infects the BIOS and Master Boot Record (MBR) of affected devices.
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Summary

Mebromi is a trojan that contains several rootkits and has been sold on underground markets since 2011. It was the first to be discovered in the wild that infects the BIOS and Master Boot Record (MBR) of affected devices.

Affected platforms

The following platforms are known to be affected:

Threat details

Mebromi infects systems via a dropper, but at the time of publication it is not known how the dropper is spread. This is likely to be via spam campaigns or malicious downloads.

The dropper checks if the system is running certain security software. It then loads a kernel mode driver to gain access to the BIOS. It checks whether the BIOS can be overwritten and makes a copy of it. Control is then passed back to the user mode component, which runs a legitimate BIOS flash tool and overwrites the BIOS with the infected version.

Whether or not the BIOS infection succeeds, the dropper then stores a copy of the partition table before infecting the MBR. This infection injects malicious code into Windows components during system startup, which will result in additional malware being downloaded. Mebromi uses a kernel mode rootkit to hide the MBR infection from the user, and this infection is restored at every system startup if the BIOS was successfully compromised.


Remediation advice

To prevent and detect an infection, ensure that:

Remediation steps

Type Step
  • A robust program of education and awareness training is delivered to users to ensure they don’t open attachments or follow links within unsolicited emails.
  • All operating systems, antivirus and other security products are kept up to date.
  • All day to day computer activities such as email and internet are performed using non-administrative accounts.
  • Strong password policies are in place and password reuse is discouraged.
  • Network, proxy and firewall logs should be monitored for suspicious activity.
  • User accounts accessed from infected machines should be reset on a clean computer.

Last edited: 17 February 2020 12:48 pm