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Detection rules › Sigma

Suspicious Unsigned Dbghelp/Dbgcore DLL Loaded

Status
test
Severity
high
Log source
product windows, category image_load
Author
Perez Diego (@darkquassar), oscd.community, Ecco
Source
github.com/SigmaHQ/sigma

Detects the load of dbghelp/dbgcore DLL (used to make memory dumps) by suspicious processes. Tools like ProcessHacker and some attacker tradecract use MiniDumpWriteDump API found in dbghelp.dll or dbgcore.dll. As an example, SilentTrynity C2 Framework has a module that leverages this API to dump the contents of Lsass.exe and transfer it over the network back to the attacker's machine.

MITRE ATT&CK coverage

TacticTechniques
Credential AccessT1003.001 OS Credential Dumping: LSASS Memory

Event coverage

ProviderEventTitle
SysmonEvent ID 7Image loaded

Rule body yaml

title: Suspicious Unsigned Dbghelp/Dbgcore DLL Loaded
id: bdc64095-d59a-42a2-8588-71fd9c9d9abc
related:
    - id: 0e277796-5f23-4e49-a490-483131d4f6e1 # Suspicious Loading
      type: similar
status: test
description: |
    Detects the load of dbghelp/dbgcore DLL (used to make memory dumps) by suspicious processes.
    Tools like ProcessHacker and some attacker tradecract use MiniDumpWriteDump API found in dbghelp.dll or dbgcore.dll.
    As an example, SilentTrynity C2 Framework has a module that leverages this API to dump the contents of Lsass.exe and transfer it over the network back to the attacker's machine.
references:
    - https://learn.microsoft.com/en-us/windows/win32/api/minidumpapiset/nf-minidumpapiset-minidumpwritedump
    - https://www.pinvoke.net/default.aspx/dbghelp/MiniDumpWriteDump.html
    - https://medium.com/@fsx30/bypass-edrs-memory-protection-introduction-to-hooking-2efb21acffd6
author: Perez Diego (@darkquassar), oscd.community, Ecco
date: 2019-10-27
modified: 2022-12-09
tags:
    - attack.credential-access
    - attack.t1003.001
logsource:
    category: image_load
    product: windows
detection:
    selection:
        ImageLoaded|endswith:
            - '\dbghelp.dll'
            - '\dbgcore.dll'
        Signed: 'false'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    ImageLoaded|endswith:
        - '\dbghelp.dll'
        - '\dbgcore.dll'
    Signed: 'false'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
ImageLoadedends_with
  • \dbgcore.dll corpus 6 (sigma 6)
  • \dbghelp.dll corpus 6 (sigma 6)
Signedeq
  • false corpus 9 (splunk 5, sigma 4)