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Once installed, GandCrab creates a registry entry so that it runs at start-up before collecting the following information:
user and computer name
presence of antivirus
processor type and architecture
Files are encrypted using the RSA algorithm, with the public and private keys generated using API calls to standard Microsoft libraries. The ransom note demands payment in Dash, a less widely used cryptocurrency.
14 Mar 2018
A new variant of GandCrab has been observed using a new file extension, .CRAB, as well as new ransom notes and Tor payment sites.
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.
Use a port scanner to confirm UDP 137, 138 and TCP 139, 445 are locked down
Ensure all affected platforms are updated in line with the Microsoft security bulletin MS17-010. Microsoft has additionally recommended updating with all security patches released within the last 60 days - internet and N3 facing systems should be prioritised. Because of the high severity of this vulnerability Microsoft has taken the highly unusual step of releasing a patch for out of support operating systems including Windows XP, Windows 8, and Windows Server 2003. For further information see Microsoft Customer guidance for WannaCry attacks
Use a vulnerability scanner (such as Nessus, OpenVas or Microsoft Baseline Security Analyser) to identify any unpatched systems.
If it is not possible to apply this patch then block SMB related ports (UDP 137, 138 and TCP 139, 445) across your organisation's network or disable SMB
If your organisation has SMB port 445 exposed on any system then review if this is operationally necessary (including the use of NetBIOS ports UDP 137 & 138 and NetBIOS over TCP/IP TCP Ports 137 & 139) as SMB and NetBIOS are both legacy protocols that may no longer be required within your environment.
If you are using SMBv1 in your environment (which is now 30 years old and lacks security features of later version) migrate to a more secure SMB version as described in the Microsoft Blog - Stop using SMB1
A new tool, capable of decrypting GandCrab versions V1, V4 and V5 files, has been released by the NoMoreRansom project. Organisations are advised that NHS Digital do not test decryption tools and that they use them at their own risk.