Detect Compile After Delivery in IBM QRadar
Adversaries may attempt to make payloads difficult to discover and analyze by delivering files to victims as uncompiled code. Text-based source code files may subvert analysis and scrutiny from protections targeting executables/binaries. These payloads will need to be compiled before execution; typically via native utilities such as csc.exe (C# compiler), ilasm.exe (.NET assembler), or GCC/MinGW. Source code payloads may also be encrypted or encoded. Threat actors including MuddyWater, Gamaredon Group, Rocke, Cardinal RAT, and DarkWatchman have used this technique to compile malware on victim systems using built-in compiler utilities.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1027 Obfuscated Files or Information
- Sub-technique
- T1027.004 Compile After Delivery
- Canonical reference
- https://attack.mitre.org/techniques/T1027/004/
QRadar Detection Query
SELECT
DATEFORMAT(devicetime, 'yyyy-MM-dd HH:mm:ss') AS event_time,
logsourcename(logsourceid) AS log_source,
sourceip,
username,
"processname" AS process_name,
"commandline" AS command_line,
"parentprocessname" AS parent_process,
CASE
WHEN LOWER("commandline") LIKE '%\temp\%' OR LOWER("commandline") LIKE '%\appdata\%' OR LOWER("commandline") LIKE '%\downloads\%' THEN 1
ELSE 0
END AS source_from_temp,
CASE
WHEN LOWER("parentprocessname") LIKE '%powershell%' OR LOWER("parentprocessname") LIKE '%wscript%'
OR LOWER("parentprocessname") LIKE '%cscript%' OR LOWER("parentprocessname") LIKE '%mshta%'
OR LOWER("parentprocessname") LIKE '%cmd%' THEN 1
ELSE 0
END AS parent_suspicious,
CASE
WHEN LOWER("commandline") NOT LIKE '%visual studio%' AND LOWER("commandline") NOT LIKE '%devenv%' THEN 1
ELSE 0
END AS no_visual_studio
FROM events
WHERE devicetime > NOW() - 86400000
AND LOGSOURCETYPEID IN (12, 13, 352)
AND eventid = 1
AND (
LOWER("processname") = 'csc.exe'
OR LOWER("processname") = 'vbc.exe'
OR LOWER("processname") = 'ilasm.exe'
OR LOWER("processname") = 'msbuild.exe'
OR LOWER("processname") = 'jsc.exe'
OR LOWER("processname") = 'cl.exe'
OR LOWER("processname") = 'gcc'
OR LOWER("processname") = 'g++'
)
AND NOT LOWER("commandline") LIKE '%winsx%'
HAVING (source_from_temp + parent_suspicious + no_visual_studio) >= 2
ORDER BY event_time DESCAQL rule targeting Sysmon EventID 1 (Process Create) for known compiler binaries executing with source files from user-writable directories, spawned from script interpreters. Suspicion scoring mirrors the SPL reference query. Maps to T1027.004.
Data Sources
Required Tables
False Positives & Tuning
- Build servers or developer VMs ingested into QRadar where msbuild/csc regularly run from AppData paths during NuGet restore and build operations
- PowerShell-based deployment scripts that invoke csc.exe to compile helper utilities as part of a legitimate bootstrapping workflow
- Security testing labs and red-team infrastructure where compilers are routinely executed by cmd.exe or PowerShell during tool preparation
Other platforms for T1027.004
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 1Compile and Execute C# Payload via csc.exe
Expected signal: Sysmon Event ID 11: payload.cs created in %TEMP%. Sysmon Event ID 1: csc.exe with /out: argument pointing to %TEMP%. Sysmon Event ID 11: compiled_payload.exe created. Sysmon Event ID 1: compiled_payload.exe execution.
- Test 2MSBuild Execution of Inline C# Task (LOLBin Abuse)
Expected signal: Sysmon Event ID 11: evil.proj created in %TEMP%. Sysmon Event ID 1: MSBuild.exe process creation with %TEMP%\evil.proj argument. The code executes within the MSBuild process itself — no separate child process for the C# code.
- Test 3Compile C Source Code with GCC (Linux/macOS)
Expected signal: Process creation events: gcc with /tmp/payload.c argument, then compiled_payload execution. Syslog/auditd: execve syscalls for gcc and the compiled binary. File creation events for /tmp/payload.c and /tmp/compiled_payload.
- Test 4PowerShell Spawning csc.exe to Compile Downloaded Source
Expected signal: Sysmon Event ID 1: powershell.exe with Set-Content and Start-Process commands. Sysmon Event ID 11: downloaded.cs and output.exe created in %TEMP%. Sysmon Event ID 1: csc.exe with parent PowerShell. Sysmon Event ID 1: output.exe executed.
References (5)
- https://attack.mitre.org/techniques/T1027/004/
- https://www.clearskysec.com/wp-content/uploads/2018/11/MuddyWater-Operations-in-Lebanon-and-Oman.pdf
- https://www.attackiq.com/2023/03/16/hiding-in-plain-sight/
- https://blog.trendmicro.com/trendlabs-security-intelligence/windows-app-runs-on-mac-downloads-info-stealer-and-adware/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1027.004/T1027.004.md
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