Detect Exploitation for Client Execution in CrowdStrike LogScale
Adversaries may exploit software vulnerabilities in client applications to execute code. This includes browser-based exploitation via drive-by compromise or spearphishing links, Office application exploitation through malicious attachments (CVE-2017-11882, CVE-2017-0262, CVE-2021-40444), and third-party application exploitation (Adobe Reader, Flash). These exploits cause vulnerable client software to execute attacker-controlled code, often spawning unexpected child processes or injecting shellcode into memory.
MITRE ATT&CK
- Tactic
- Execution
- Technique
- T1203 Exploitation for Client Execution
- Canonical reference
- https://attack.mitre.org/techniques/T1203/
LogScale Detection Query
#event_simpleName = ProcessRollup2
| ParentBaseFileName = /(?i)^(winword|excel|powerpnt|outlook|mspub|visio|onenote|msaccess|chrome|firefox|msedge|iexplore|opera|brave|acrord32|acrobat|foxitpdfeditor|sumatrapdf)\.exe$/
| FileName = /(?i)^(cmd|powershell|pwsh|wscript|cscript|mshta|rundll32|regsvr32|certutil|bitsadmin|msbuild|installutil|regasm|regsvcs|schtasks|wmic|msiexec)\.exe$/
| ExploitVector := case {
ParentBaseFileName = /(?i)(winword|excel|powerpnt|outlook|mspub|visio|onenote|msaccess)\.exe/ => "Office Application";
ParentBaseFileName = /(?i)(chrome|firefox|msedge|iexplore|opera|brave)\.exe/ => "Browser";
ParentBaseFileName = /(?i)(acrord32|acrobat|foxit|sumatrapdf)\.exe/ => "PDF Reader";
* => "Other"
}
| HighRisk := if(FileName = /(?i)(powershell|pwsh|mshta|regsvr32|rundll32|wscript|cscript)\.exe$/, "true", "false")
| select([_time, ComputerName, UserName, ExploitVector, ParentBaseFileName, ParentCommandLine, FileName, CommandLine, TargetProcessId, ContextProcessId, HighRisk])
| sort(field=_time, order=desc)CrowdStrike LogScale (Falcon) CQL query detecting T1203 client exploitation using ProcessRollup2 Falcon sensor events. Matches ParentBaseFileName (the direct parent process, a client application) against Office suite, browser, and PDF reader families, and FileName (the spawned child) against LOLBins and script interpreters. ProcessRollup2 events include accurate parent-child process lineage from kernel-level telemetry. ExploitVector classification and HighRisk flag support analyst triage prioritization in Falcon Investigate or LogScale dashboards.
Data Sources
Required Tables
False Positives & Tuning
- Helpdesk or RMM tool automation that uses Office COM interop to remotely invoke PowerShell or cmd.exe for managed endpoint diagnostics, software inventory, or configuration remediation on corporate workstations
- Enterprise browser extensions designed for privileged access management, hardware security key authentication, or smart card middleware that launch rundll32.exe to communicate with local PKCS11 or CCID drivers
- Adobe Acrobat Pro or Foxit enterprise license management and activation scripts that call certutil.exe or wscript.exe during seat management, certificate-based DRM enforcement, or volume license renewal tasks
Other platforms for T1203
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Simulate Office Exploitation — Equation Editor Child Process
Expected signal: Sysmon Event ID 1: Process Create with ParentImage containing eqnedt32.exe and Image=cmd.exe. Security Event ID 4688 with similar parent/child relationship if command line auditing enabled.
- Test 2Office Application Spawning PowerShell via Macro Simulation
Expected signal: Sysmon Event ID 1: Process Create chain showing cmd.exe spawning powershell.exe. The detection focuses on the child process spawning pattern. PowerShell ScriptBlock Log Event ID 4104 will record the Write-Output command.
- Test 3Browser Renderer Process Spawning Cmd
Expected signal: Sysmon Event ID 1: Process Create for cmd.exe with subsequent net.exe and whoami.exe child processes. This represents the reconnaissance commands commonly executed immediately following successful browser exploitation.
- Test 4Mshta Spawned from Office Context (CVE-2021-40444 Pattern)
Expected signal: Sysmon Event ID 1: Process Create for mshta.exe. In real exploitation this process would have a parent of winword.exe or excel.exe. Security Event ID 4688 will also record the mshta.exe launch with command line arguments.
References (8)
- https://attack.mitre.org/techniques/T1203/
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2017-11882
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40444
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1203/T1203.md
- https://www.mandiant.com/resources/blog/evasive-attacker-leverages-solarwinds-supply-chain-compromises-with-sunburst-backdoor
- https://github.com/SigmaHQ/sigma/tree/master/rules/windows/process_creation
- https://learn.microsoft.com/en-us/defender-endpoint/advanced-hunting-deviceprocessevents-table
- https://www.sentinelone.com/blog/agent-tesla-old-rat-uses-new-tricks-to-stay-on-top/
Unlock Pro Content
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