Unsigned DLL Side-Loading from a Suspicious Folder

Identifies a Windows trusted program running from locations often abused by adversaries to masquerade as a trusted program and loading a recently dropped DLL. This behavior may indicate an attempt to evade defenses via side-loading a malicious DLL within the memory space of a signed processes.

Rule type: eql

Rule indices:

logs-endpoint.events.*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References: None

Tags:

Elastic
Host
Windows
Threat Detection
Defense Evasion

Version: 1

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

edit

Rule query

edit

library where

 process.code_signature.trusted == true and

 (dll.Ext.relative_file_creation_time <= 500 or dll.Ext.relative_file_name_modify_time <= 500) and

  not dll.code_signature.status : ("trusted", "errorExpired", "errorCode_endpoint*", "errorChaining") and

      /* Suspicious Paths */
      dll.path : ("?:\\PerfLogs\\*.dll",
                  "?:\\Users\\*\\Pictures\\*.dll",
                  "?:\\Users\\*\\Music\\*.dll",
                  "?:\\Users\\Public\\*.dll",
                  "?:\\Users\\*\\Documents\\*.dll",
                  "?:\\Windows\\Tasks\\*.dll",
                  "?:\\Windows\\System32\\Tasks\\*.dll",
                  "?:\\Intel\\*.dll",
                  "?:\\AMD\\Temp\\*.dll",
                  "?:\\Windows\\AppReadiness\\*.dll",
                  "?:\\Windows\\ServiceState\\*.dll",
                  "?:\\Windows\\security\\*.dll",
		  "?:\\Windows\\System\\*.dll",
                  "?:\\Windows\\IdentityCRL\\*.dll",
                  "?:\\Windows\\Branding\\*.dll",
                  "?:\\Windows\\csc\\*.dll",
                  "?:\\Windows\\DigitalLocker\\*.dll",
                  "?:\\Windows\\en-US\\*.dll",
                  "?:\\Windows\\wlansvc\\*.dll",
                  "?:\\Windows\\Prefetch\\*.dll",
                  "?:\\Windows\\Fonts\\*.dll",
                  "?:\\Windows\\diagnostics\\*.dll",
                  "?:\\Windows\\TAPI\\*.dll",
                  "?:\\Windows\\INF\\*.dll",
                  "?:\\windows\\tracing\\*.dll",
                  "?:\\windows\\IME\\*.dll",
                  "?:\\Windows\\Performance\\*.dll",
                  "?:\\windows\\intel\\*.dll",
                  "?:\\windows\\ms\\*.dll",
                  "?:\\Windows\\dot3svc\\*.dll",
                  "?:\\Windows\\ServiceProfiles\\*.dll",
                  "?:\\Windows\\panther\\*.dll",
                  "?:\\Windows\\RemotePackages\\*.dll",
                  "?:\\Windows\\OCR\\*.dll",
                  "?:\\Windows\\appcompat\\*.dll",
                  "?:\\Windows\\apppatch\\*.dll",
                  "?:\\Windows\\addins\\*.dll",
                  "?:\\Windows\\Setup\\*.dll",
                  "?:\\Windows\\Help\\*.dll",
                  "?:\\Windows\\SKB\\*.dll",
                  "?:\\Windows\\Vss\\*.dll",
                  "?:\\Windows\\Web\\*.dll",
                  "?:\\Windows\\servicing\\*.dll",
                  "?:\\Windows\\CbsTemp\\*.dll",
                  "?:\\Windows\\Logs\\*.dll",
                  "?:\\Windows\\WaaS\\*.dll",
                  "?:\\Windows\\twain_32\\*.dll",
                  "?:\\Windows\\ShellExperiences\\*.dll",
                  "?:\\Windows\\ShellComponents\\*.dll",
                  "?:\\Windows\\PLA\\*.dll",
                  "?:\\Windows\\Migration\\*.dll",
                  "?:\\Windows\\debug\\*.dll",
                  "?:\\Windows\\Cursors\\*.dll",
                  "?:\\Windows\\Containers\\*.dll",
                  "?:\\Windows\\Boot\\*.dll",
                  "?:\\Windows\\bcastdvr\\*.dll",
                  "?:\\Windows\\TextInput\\*.dll",
                  "?:\\Windows\\schemas\\*.dll",
                  "?:\\Windows\\SchCache\\*.dll",
                  "?:\\Windows\\Resources\\*.dll",
                  "?:\\Windows\\rescache\\*.dll",
                  "?:\\Windows\\Provisioning\\*.dll",
                  "?:\\Windows\\PrintDialog\\*.dll",
                  "?:\\Windows\\PolicyDefinitions\\*.dll",
                  "?:\\Windows\\media\\*.dll",
                  "?:\\Windows\\Globalization\\*.dll",
                  "?:\\Windows\\L2Schemas\\*.dll",
                  "?:\\Windows\\LiveKernelReports\\*.dll",
                  "?:\\Windows\\ModemLogs\\*.dll",
                  "?:\\Windows\\ImmersiveControlPanel\\*.dll",
                  "?:\\$Recycle.Bin\\*.dll") and

	 /* DLL loaded from the process.executable current directory */
	 endswith~(substring(dll.path, 0, length(dll.path) - (length(dll.name) + 1)), substring(process.executable, 0, length(process.executable) - (length(process.name) + 1)))

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Hijack Execution Flow
- ID: T1574
- Reference URL: https://attack.mitre.org/techniques/T1574/
Sub-technique:
- Name: DLL Side-Loading
- ID: T1574.002
- Reference URL: https://attack.mitre.org/techniques/T1574/002/

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