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Elastic Docs ›Elastic Security [8.13] ›Downloadable rule update v8.13.18

Unsigned DLL Side-Loading from a Suspicious Folder

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Unsigned DLL Side-Loading from a Suspicious Folder

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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.library-*

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:

Tags:

  • Domain: Endpoint
  • OS: Windows
  • Use Case: Threat Detection
  • Tactic: Defense Evasion
  • Data Source: Elastic Defend

Version: 9

Rule authors:

  • Elastic

Rule license: Elastic License v2

Setup

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Setup

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define event.ingested and default fallback for EQL rules was not added until version 8.2. Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate event.ingested to @timestamp. For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html

Rule query

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library where host.os.type == "windows" and

 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&CKTM

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