Detect Indirect Command Execution in Splunk
Adversaries may abuse utilities that allow for command execution to bypass security restrictions that limit the use of command-line interpreters. Various Windows utilities may be used to execute commands, possibly without invoking cmd.exe directly. Tools such as Forfiles, the Program Compatibility Assistant (pcalua.exe), Windows Subsystem for Linux (WSL via wsl.exe or bash.exe), Scriptrunner.exe, and ssh.exe may invoke the execution of programs and commands from a scripting interpreter, Run window, or via scripts. Adversaries use these features for Defense Evasion, specifically to perform arbitrary execution while subverting detections and Group Policy controls that restrict cmd.exe usage or block certain file extensions. Real-world actors including Lazarus Group (forfiles for .htm execution), Revenge RAT (forfiles for command execution), and RedCurl (pcalua.exe for binary obfuscation) have demonstrated operational use of this technique.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1202 Indirect Command Execution
- Canonical reference
- https://attack.mitre.org/techniques/T1202/
SPL Detection Query
index=wineventlog sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=1
| eval Image=lower(Image)
| eval CommandLine=lower(CommandLine)
| eval ParentImage=lower(ParentImage)
// Identify indirect execution method
| eval IsForfiles=if(match(Image, "forfiles\.exe$") AND match(CommandLine, "(/c|/c\s)"), 1, 0)
| eval IsPcalua=if(match(Image, "pcalua\.exe$") AND match(CommandLine, "(-a|-i)\s"), 1, 0)
| eval IsScriptrunner=if(match(Image, "scriptrunner\.exe$") AND match(CommandLine, "(-appcompat|/appcompat|\.exe|\.bat|\.ps1|\.cmd)"), 1, 0)
| eval IsWsl=if((match(Image, "wsl\.exe$") OR match(Image, "bash\.exe$")) AND match(CommandLine, "(-e\s|--exec|-c\s|cmd\.exe|powershell|net\.exe|curl|wget|\snc\s|ncat|python|/mnt/c|base64)"), 1, 0)
| eval IsSshProxy=if(match(Image, "ssh\.exe$") AND match(CommandLine, "(proxycommand|localcommand|permitlocalcommand)"), 1, 0)
// Compute execution method label
| eval ExecutionMethod=case(
IsForfiles=1, "Forfiles",
IsPcalua=1, "PcaluaBypass",
IsScriptrunner=1, "Scriptrunner",
IsWsl=1, "WSL",
IsSshProxy=1, "SSH-ProxyCommand",
true(), null()
)
| where isnotnull(ExecutionMethod)
// Elevate suspicion if parent is Office, script hosts, or suspicious loaders
| eval SuspiciousParent=if(match(ParentImage, "(winword\.exe|excel\.exe|outlook\.exe|powerpnt\.exe|mshta\.exe|wscript\.exe|cscript\.exe|explorer\.exe|rundll32\.exe|regsvr32\.exe|msiexec\.exe)"), 1, 0)
| eval SuspicionScore=IsForfiles + IsPcalua + IsScriptrunner + IsWsl + IsSshProxy + SuspiciousParent
| table _time, host, User, Image, CommandLine, ParentImage, ParentCommandLine, ExecutionMethod, SuspiciousParent, SuspicionScore
| sort - _timeDetects indirect command execution via LOLBins using Sysmon Event ID 1 (Process Creation). Evaluates five execution vectors: forfiles.exe with /c flag, pcalua.exe with -a/-i flags, scriptrunner.exe with appcompat arguments, wsl.exe/bash.exe invoking Windows-side commands or accessing the filesystem, and ssh.exe abusing ProxyCommand/LocalCommand options. Assigns a suspicion score that increases when the launching parent is itself a known suspicious process (Office apps, script hosts, rundll32), enabling analysts to prioritize high-confidence alerts.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Legitimate administrative use of forfiles.exe for batch file operations, directory traversal, or scheduled maintenance scripts (e.g., deleting files older than N days)
- WSL (wsl.exe/bash.exe) activity from developers who legitimately use Linux tools and access the Windows filesystem via /mnt/c in their daily workflows
- System compatibility infrastructure invoking pcalua.exe when users launch legacy applications that trigger Program Compatibility Assistant automatically
- SSH client usage with ProxyCommand set in ~/.ssh/config for legitimate jump-host configurations or tunneling through bastion hosts
- Scriptrunner.exe invoked by application shims during compatibility testing or software packaging processes
Other platforms for T1202
Testing Methodology
Validate this detection against 5 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 1Forfiles Indirect Command Execution via cmd.exe
Expected signal: Sysmon Event ID 1: Process Create for forfiles.exe with CommandLine containing '/c cmd /c whoami'. Subsequent Sysmon Event ID 1: Process Create for cmd.exe with ParentImage=forfiles.exe. Sysmon Event ID 11: File Create for the output file in %TEMP%. Security Event ID 4688 (if command line auditing enabled) for both forfiles.exe and cmd.exe.
- Test 2Pcalua.exe Proxy Execution of Calculator (Binary Launch Bypass)
Expected signal: Sysmon Event ID 1: Process Create for pcalua.exe with CommandLine 'pcalua.exe -a calc.exe'. Sysmon Event ID 1: Process Create for calc.exe with ParentImage=pcalua.exe. Security Event ID 4688 for both processes. The parent-child relationship (pcalua → calc) is the key telemetry indicator.
- Test 3WSL Indirect Execution of Windows Binary via /mnt/c
Expected signal: Sysmon Event ID 1: Process Create for wsl.exe with CommandLine containing '-e /bin/sh -c cmd.exe'. Child process creation for cmd.exe or the shell spawned within WSL context. Sysmon Event ID 11: File Create for the output file at C:\Users\Public\. The wsl.exe parent attribution is the key telemetry.
- Test 4Forfiles Execute PowerShell Payload (Simulated Lazarus Group Pattern)
Expected signal: Sysmon Event ID 1: Process Create for forfiles.exe with CommandLine containing 'powershell.exe'. Subsequent Sysmon Event ID 1: Process Create for powershell.exe with ParentImage=forfiles.exe. PowerShell Script Block Logging Event ID 4104 showing the Get-Date command. Sysmon Event ID 11 for the output file.
- Test 5SSH.exe ProxyCommand Arbitrary Command Execution
Expected signal: Sysmon Event ID 1: Process Create for ssh.exe with CommandLine containing 'ProxyCommand' and 'cmd.exe'. Sysmon Event ID 1: Child process create for cmd.exe with ParentImage=ssh.exe. Sysmon Event ID 11: File Create for the output file. Network connection attempt Event ID 3 to localhost:22 (will fail). The ProxyCommand string in the SSH command line is the primary detection indicator.
References (13)
- https://attack.mitre.org/techniques/T1202/
- https://community.rsa.com/community/products/netwitness/blog/2017/08/14/are-you-looking-out-for-forfilesexe-if-you-are-watching-for-cmdexe
- https://x.com/vector_sec/status/896049052642533376
- https://x.com/Evi1cg/status/935027922397573120
- https://secureteam.co.uk/2023/01/08/windows-error-reporting-tool-abused-to-load-malware/
- https://www.bleepingcomputer.com/news/security/hackers-abuse-windows-error-reporting-tool-to-deploy-malware/
- https://ss64.com/nt/scriptrunner.html
- https://cyble.com/blog/threat-actor-targets-manufacturing-industry-with-malware/
- https://lolbas-project.github.io/lolbas/Binaries/Forfiles/
- https://lolbas-project.github.io/lolbas/Binaries/Pcalua/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1202/T1202.md
- https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_lolbin_forfiles.yml
- https://learn.microsoft.com/en-us/defender-endpoint/advanced-hunting-deviceprocessevents-table
Unlock Pro Content
Get the full detection package for T1202 including response playbook, investigation guide, and atomic red team tests.