Add Debugger Entry To AeDebug For Persistence

Hunt Hypothesis

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

Detection Rule

Sigma (Original)

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

KQL (Azure Sentinel)

imRegistry
| where (RegistryKey contains "\\SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug\\Debugger" and RegistryValueData endswith ".dll") and (not(RegistryValueData =~ "\"C:\\WINDOWS\\system32\\vsjitdebugger.exe\" -p %ld -e %ld -j 0x%p"))

KQL (Microsoft 365 Defender)

DeviceRegistryEvents
| where (RegistryKey contains "\\SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug\\Debugger" and RegistryValueData endswith ".dll") and (not(RegistryValueData =~ "\"C:\\WINDOWS\\system32\\vsjitdebugger.exe\" -p %ld -e %ld -j 0x%p"))

Required Data Sources

False Positive Guidance

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

MITRE ATT&CK Context

• Tactic: Persistence

References

• https://persistence-info.github.io/Data/aedebug.html
• https://learn.microsoft.com/en-us/windows/win32/debug/configuring-automatic-debugging
• SigmaHQ Rule