CryptON Ransomware

CryptON is a ransomware tool that is deployed in attacks targeting computers with Remote Desktop Services (RDS) exposed to the Internet.

Threat ID:: CC-2425
Category:: Ransomware
Threat Severity:: Medium
Threat Vector:
Published:: 24 May 2018 12:00 AM

Report a cyber attack: call 0300 303 5222 or email [email protected]

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Summary

CryptON is a ransomware tool that is deployed in attacks targeting computers with Remote Desktop Services (RDS) exposed to the Internet.

Affected platforms

The following platforms are known to be affected:

Microsoft Windows

Microsoft Windows - All versions

Threat details

The threat actors exploit RDS and then execute CryptON. The ransomware encrypts files and appends filenames with a [email protected] extension. Shadow Copies are deleted in most instances, but they are occasionally left untouched.

A file containing a ransom note is created in every folder where files have been encrypted. This demands that the user connects to a Tor website, from which they can communicate with the attacker and receive payment instructions.

There is no known method for decrypting files that have been encrypted by the latest variant of CryptON.

Remediation steps

Type	Step
	If Remote Desktop Services (RDS) are not used, then ensure port 3389 (TCP/UDP) is blocked at your internet firewall. If RDS is used, then: Only allow access for authorised RDS users. Enforce strong password policies. Enforce multi-factor authentication. Don't allow RDS access for privileged user accounts. Don’t use generic accounts. Set user accounts with an expiry date. Audit user accounts periodically. Only allow point-to-point connections from specific IP addresses where feasible. Ensure Transport Layer Security (TLS) is up-to-date. Log and monitor all RDS activity and investigate unusual behaviour. Consider only allowing RDS for authorised virtual private network (VPN) connections. If a device 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, anti-virus 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 affected device and 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 device). 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.

Type

Step

If Remote Desktop Services (RDS) are not used, then ensure port 3389 (TCP/UDP) is blocked at your internet firewall. If RDS is used, then:

Only allow access for authorised RDS users.
Enforce strong password policies.
Enforce multi-factor authentication.
Don't allow RDS access for privileged user accounts.
Don’t use generic accounts.
Set user accounts with an expiry date.
Audit user accounts periodically.
Only allow point-to-point connections from specific IP addresses where feasible.
Ensure Transport Layer Security (TLS) is up-to-date.
Log and monitor all RDS activity and investigate unusual behaviour.
Consider only allowing RDS for authorised virtual private network (VPN) connections.

If a device 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, anti-virus 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 affected device and 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 device).

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.

Last edited: 17 February 2020 12:41 pm