NEFILIM Ransomware

If a device on your network becomes infected with ransomware it will begin encrypting files the logged-in user has permission to modify, which may also include remote files on network locations. The only guaranteed way to recover from a ransomware infection is to restore all affected files from their most recent backup.

Please note that NCSC maintains guidance for securely configuring a wide range of end user device (EUD) platforms. For further details refer to their end user device security guidance pages.

To reduce the likelihood of infection by ransomware, NHS Digital advises that:

• Secure configurations are applied to all devices.
• Security updates are applied at the earliest opportunity.
• Tamper protection settings in security products are enabled where available.
• Obsolete platforms are segregated from the rest of the network.
• IT usage policies are reinforced by regular training to ensure all users know not to open unsolicited links or attachments.
• Multi-factor authentication (MFA) and lockout policies are used where practicable, especially for administrative accounts.
• Administrative accounts are only used for necessary purposes.
• Remote administration services use strongly encrypted protocols and only accept connections from authorised users or locations.
• Systems are continuously monitored, and unusual activity is investigated, so that a compromise of the network can be detected as early as possible.

To limit the impact of a ransomware infection, NHS Digital advises that:

• Critical data is frequently saved in multiple backup locations.
• At least one backup is kept offline at any time (separated from live systems).
• Backups and incident recovery plans are tested to ensure that data can be restored when needed.
• User account permissions for modifying data are regularly reviewed and restricted to the minimum necessary.
• Infected systems are disconnected from the network and powered down as soon as practicable.
• Any user account credentials that may have been compromised should be reset on a clean device.
• Where infected systems cannot be quarantined with confidence, then an affected organisation should disconnect from national networks to limit propagation.

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

• Ensure network level authentication is enabled.
• Only allow access for authorised RDP users.
• Enforce strong password policies.
• Enforce multi-factor authentication.
• Don't allow RDP 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 RDP activity and investigate unusual behaviour.
• Consider only allowing RDP for authorised virtual private network (VPN) connections.