Detect Exploitation for Client Execution in Splunk
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/
SPL Detection Query
index=wineventlog sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=1
| eval ParentImageLower=lower(ParentImage)
| eval ImageLower=lower(Image)
| eval ExploitVector=case(
match(ParentImageLower, "(winword|excel|powerpnt|outlook|mspub|visio|onenote|msaccess)\.exe"), "Office Application",
match(ParentImageLower, "(chrome|firefox|msedge|iexplore|opera|brave)\.exe"), "Browser",
match(ParentImageLower, "(acrord32|acrobat|foxit|sumatrapdf)\.exe"), "PDF Reader",
match(ParentImageLower, "eqnedt32\.exe"), "Equation Editor",
true(), "Other"
)
| where ExploitVector!="Other"
| eval SuspiciousChild=if(match(ImageLower, "(cmd|powershell|pwsh|wscript|cscript|mshta|rundll32|regsvr32|certutil|bitsadmin|msbuild|installutil|regasm|regsvcs|schtasks|wmic|msiexec)\.exe"), 1, 0)
| where SuspiciousChild=1
| eval HighRisk=if(match(ImageLower, "(powershell|pwsh|mshta|regsvr32|rundll32|wscript|cscript)\.exe"), 1, 0)
| table _time, host, User, ExploitVector, ParentImage, ParentCommandLine, Image, CommandLine, CurrentDirectory, HighRisk
| sort - _timeDetects exploitation for client execution using Sysmon Event ID 1 (Process Creation). Identifies suspicious child processes spawned by Office applications, browsers, PDF readers, and Equation Editor. Flags processes commonly used in post-exploitation payloads. The ExploitVector field identifies the likely exploit delivery mechanism for faster analyst triage.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Office macros legitimately launching PowerShell or cmd.exe for automation tasks
- Browser integrations spawning helper processes for download handling or protocol handlers
- PDF readers opening embedded Office documents that in turn spawn child processes
- Equation Editor spawned during normal document rendering on unpatched Office installations
- Developer tools or terminal integrations within browsers
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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