Add Debugger Entry To AeDebug For Persistence

Status: test
Severity: medium
Log source: category registry_set, product windows
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects when an attacker adds a new "Debugger" value to the "AeDebug" key in order to achieve persistence which will get invoked when an application crashes

Known false positives

Legitimate use of the key to setup a debugger. Which is often the case on developers machines

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	No specific technique

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 13: RegistryEvent (Value Set)

Rule body

title: Add Debugger Entry To AeDebug For Persistence
id: 092af964-4233-4373-b4ba-d86ea2890288
status: test
description: Detects when an attacker adds a new "Debugger" value to the "AeDebug" key in order to achieve persistence which will get invoked when an application crashes
references:
    - https://persistence-info.github.io/Data/aedebug.html
    - https://learn.microsoft.com/en-us/windows/win32/debug/configuring-automatic-debugging
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-07-21
modified: 2023-08-17
tags:
    - attack.persistence
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|contains: '\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug\Debugger'
        Details|endswith: '.dll'
    filter:
        Details: '"C:\WINDOWS\system32\vsjitdebugger.exe" -p %ld -e %ld -j 0x%p'
    condition: selection and not filter
falsepositives:
    - Legitimate use of the key to setup a debugger. Which is often the case on developers machines
level: medium

Stages and Predicates

Stage 0: `condition`

selection and not filter

Stage 1: `selection`

selection:
    TargetObject|contains: '\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug\Debugger'
    Details|endswith: '.dll'

Stage 2: `not filter`

filter:
    Details: '"C:\WINDOWS\system32\vsjitdebugger.exe" -p %ld -e %ld -j 0x%p'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Details`	eq	`"C:\WINDOWS\system32\vsjitdebugger.exe" -p %ld -e %ld -j 0x%p`	`excludes:Details`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Details`	ends_with	`.dll` corpus 9 (sigma 4, elastic 4, splunk 1)	`field:"Details" kind:ends_with value:".dll"`
`TargetObject`	match	`\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug\Debugger`	`field:"TargetObject" kind:match value:"\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug\Debugger"`