ONI And MBR-ONI Ransomware

ONI ransomware and its bootkit variant MBR-ONI have been seen being used in targeted attacks. The ransomware was used to cover up evidence of a more sophisticated attack.

In previous ONI ransomware attacks the method of infection is a phishing email that has zip file attachment containing a macro that downloads a remote administration tool. Once the attackers had access and had finished wiping the logs of their activity, they would install ONI or MBR-ONI onto the network.

ONI can encrypt files on removable media and network drives. MBR-ONI has been mainly targeted at Active Directory servers. The code for ONI does allow recovery of the encrypted disk if the correct decryption key is applied.

Affected Platforms

Microsoft Windows – All Versions


If a computer on your network becomes infected with ransomware it will begin encrypting local machine files and files on any network the logged-in user has permission to access. For system administration accounts this may include backup storage locations.

To avoid becoming infected with ransomware, ensure that:

  • 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 and that permissions are always assigned on the basis of least privilege.

Identifying the source of infection:

Identifying the infected machine and unplugging / disconnecting or quarantining it from the network is essential to damage limitation.

  • Users should immediately report infections to their IT support provider, disconnect their network cable and power the computer down.
  • File auditing should be enabled and file server logs should be monitored to detect signs of unauthorised encryption and allow the source of encryption to be identified (i.e. the infected PC).

To limit the damage of ransomware and enable recovery:

All critical data must be backed up, and these backups must be sufficiently protected/kept out of reach of ransomware.

  • Multiple backups should be created including at least one off-network backup (e.g. to tape).

Duncan is a technology professional with over 20 years experience of working in various IT roles. He also has a wide range of other skills in radio, electronics and telecommunications.

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