Unsigned Image Loaded Into lsass.exe (Windows)

Alerts on image loads into lsass.exe where the loaded image is unsigned.

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unsigned-image-loaded-into-lsass-exe-windows-857c8db3

title: Unsigned Image Loaded Into lsass.exe (Windows)
id: 5872802f-1fcb-4d0b-8a4e-877673c6a381
status: test
description: This rule flags instances where an image is loaded into the lsass.exe process and is marked as unsigned. Unsigned modules inside LSASS are a common indicator of credential access activity, since attackers may inject code to intercept credentials or manipulate authentication. The detection relies on Windows image-load telemetry that includes the target process name and a signed/unsigned attribute.
references:
  - https://www.slideshare.net/heirhabarov/hunting-for-credentials-dumping-in-windows-environment
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/image_load/image_load_lsass_unsigned_image_load.yml
author: Teymur Kheirkhabarov, oscd.community, Huntrule Team
date: 2019-10-22
modified: 2021-11-27
tags:
  - attack.credential-access
  - attack.t1003.001
logsource:
  category: image_load
  product: windows
detection:
  selection:
    Image|endswith: \lsass.exe
    Signed: "false"
  condition: selection
falsepositives:
  - Valid user connecting using RDP
level: medium
license: DRL-1.1
related:
  - id: 857c8db3-c89b-42fb-882b-f681c7cf4da2
    type: derived

What it detects

This rule flags instances where an image is loaded into the lsass.exe process and is marked as unsigned. Unsigned modules inside LSASS are a common indicator of credential access activity, since attackers may inject code to intercept credentials or manipulate authentication. The detection relies on Windows image-load telemetry that includes the target process name and a signed/unsigned attribute.

Known false positives

Valid user connecting using RDP

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.