New Cobra Crysis Ransomware Variant Released

A new variant of the Crysis ransomware, known as Cobra, has appeared that uses an encryption method that renders files unrecoverable.

Threat ID:: CC-1793
Category:: Ransomware
Threat Severity:: Medium
Threat Vector:
Published:: 16 November 2017 12:00 AM

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Summary

A new variant of the Crysis ransomware, known as Cobra, has appeared that uses an encryption method that renders files unrecoverable.

Affected platforms

The following platforms are known to be affected:

Microsoft Windows

Microsoft Windows - All Versions

Threat details

Previously, Crysis was delivered by Remote Desktop Protocol (RDP) brute-force attack, although it is unclear how this new variant is being distributed. Once installed Cobra scans for data files on local drives, mapped network drives and unmapped network shares before encrypting them. It will then seek to delete all backups and shadow volume copies.

It is not possible to decrypt .cobra files at present, with the only way to restore files being a separate backup.

Remediation steps

Type	Step
	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. Your organisation adopts a holistic all round approach to Cyber Security as advocated by the 10 Steps To Cyber Security. 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). The only guaranteed way to recover from a ransomware infection is to restore all affected files from their most recent backup. Additionally, administrators are encouraged to review their RDP policies to ensure these are sufficient to protect against possible attack.

Type

Step

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.
Your organisation adopts a holistic all round approach to Cyber Security as advocated by the 10 Steps To Cyber Security.

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).

The only guaranteed way to recover from a ransomware infection is to restore all affected files from their most recent backup.

Additionally, administrators are encouraged to review their RDP policies to ensure these are sufficient to protect against possible attack.

Last edited: 11 January 2022 4:45 pm