Detect Exploitation for Client Execution in Elastic Security
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/
Elastic Detection Query
process where event.type == "start" and
process.parent.name : (
"winword.exe", "excel.exe", "powerpnt.exe", "outlook.exe",
"mspub.exe", "visio.exe", "onenote.exe", "msaccess.exe",
"chrome.exe", "firefox.exe", "msedge.exe", "iexplore.exe",
"opera.exe", "brave.exe",
"acrord32.exe", "acrobat.exe", "foxitpdfeditor.exe", "sumatrapdf.exe"
) and
process.name : (
"cmd.exe", "powershell.exe", "pwsh.exe", "wscript.exe", "cscript.exe",
"mshta.exe", "rundll32.exe", "regsvr32.exe", "certutil.exe", "bitsadmin.exe",
"msbuild.exe", "installutil.exe", "regasm.exe", "regsvcs.exe",
"schtasks.exe", "at.exe", "wmic.exe", "msiexec.exe"
)Detects T1203 Exploitation for Client Execution using Elastic EQL process lineage correlation. Identifies LOLBins, script interpreters, and high-risk living-off-the-land executables spawned as direct child processes of Office applications, web browsers, or PDF readers — covering drive-by browser compromise, malicious document exploitation (CVE-2017-11882, CVE-2021-40444), and third-party reader abuse. The parent-child EQL match ensures low false positive rates by requiring an exact process ancestry relationship rather than loose keyword matching.
Data Sources
Required Tables
False Positives & Tuning
- Macro-enabled Office templates used by IT or finance teams that invoke cmd.exe or PowerShell for approved administrative automation such as report generation, data export, or SharePoint integration
- Enterprise browser native messaging extensions (password managers, enterprise SSO bridges, or hardware token middleware) that spawn rundll32.exe or msiexec.exe during plugin installation or credential operations
- PDF reader JavaScript actions in interactive enterprise forms that call certutil.exe or wscript.exe for certificate validation, base64 decoding, or document submission workflow processing
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/
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