Microsoft Windows Machine Account NTLM Coercion via Authenticated LSARPC Spoofing

Block remote EFSRPC functionality with RPC Filters

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If Microsoft Encrypted File System Remote Protocol (MS-EFSRPC) is not required, administrators should block the remote EFSRPC functionality on the vulnerable host using RPC filters.

1. Create a text file with the following content:

   rpc
   filter
   add rule layer=um actiontype=block
   add condition field=if_uuid matchtype=equal data=c681d488-d850-11d0-8c52-00c04fd90f7e
   add filteradd rule layer=um actiontype=block
   add condition field=if_uuid matchtype=equal data=df1941c5-fe89-4e79-bf10-463657acf44d
   add filterquit
   

2. Use the netsh command line utility to import the RPC filter from an elevated administrator prompt: netsh -f <FILTER_FILE_NAME>
3. To confirm the filters are in place, you can view the current RPC filters using the following command: netsh rpc filter show filter

See CERT Coordination Center Vulnerability Note:#405600 for additional details.