Detect Dynamic API Resolution in IBM QRadar
Adversaries may obfuscate then dynamically resolve API functions called by their malware in order to conceal malicious functionalities and impair defensive analysis. API functions called by malware leave static artifacts such as strings in payload files and in the Import Address Table (IAT). To avoid static analysis, adversaries use dynamic API resolution: hashes of function names are stored in malware in lieu of literal strings, and malware uses GetProcAddress() and LoadLibrary() to manually reproduce the linking process. Threat actors including Mustang Panda, Lazarus Group, Latrodectus, Bazar, Brute Ratel C4, TONESHELL, PlugX, Raccoon Stealer, AvosLocker, and CHIMNEYSWEEP use this technique.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1027 Obfuscated Files or Information
- Sub-technique
- T1027.007 Dynamic API Resolution
- Canonical reference
- https://attack.mitre.org/techniques/T1027/007/
QRadar Detection Query
SELECT
LOGSOURCEADDRESS(logsourceid) AS hostname,
"SourceImage" AS process_path,
COUNT(DISTINCT "ImageLoaded") AS core_dll_count,
MIN(starttime) AS first_seen,
MAX(starttime) AS last_seen
FROM events
WHERE
LOGSOURCETYPEID(logsourceid) ILIKE '%sysmon%'
AND eventid = 7
AND (
"ImageLoaded" ILIKE '%\\kernel32.dll'
OR "ImageLoaded" ILIKE '%\\kernelbase.dll'
OR "ImageLoaded" ILIKE '%\\ntdll.dll'
)
AND "SourceImage" NOT ILIKE 'C:\\Windows\\%'
AND "SourceImage" NOT ILIKE 'C:\\Program Files\\%'
AND "SourceImage" NOT ILIKE 'C:\\Program Files (x86)\\%'
AND "SourceImage" IS NOT NULL
AND "SourceImage" NOT ILIKE ''
LAST 1440 MINUTES
GROUP BY
hostname,
process_path
HAVING core_dll_count >= 1
ORDER BY core_dll_count ASCQRadar AQL query detecting dynamic API resolution via Sysmon Event ID 7 (Image Load) records. Correlates core Windows DLL loads (kernel32.dll, kernelbase.dll, ntdll.dll) against the initiating process path, filtering out loads originating from standard Windows directories. Processes from unexpected paths with these low-level DLL loads are indicative of malware using GetProcAddress-based API resolution to evade static import analysis.
Data Sources
Required Tables
False Positives & Tuning
- Custom in-house enterprise applications deployed to non-standard paths (e.g., E:\CompanyApps\) that legitimately load kernel32.dll or ntdll.dll as part of normal Windows process initialization
- Portable software bundles distributed via network shares or removable drives that execute outside Program Files and require core system DLL loading at runtime
- Security and monitoring agents (SIEM forwarders, EDR sensors) installed in administrator-defined custom directories that instrument DLL loading for telemetry purposes
Other platforms for T1027.007
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 1Demonstrate GetProcAddress Dynamic API Resolution in PowerShell
Expected signal: Sysmon Event ID 1: PowerShell process creation with Add-Type and DllImport. PowerShell ScriptBlock Log Event ID 4104: the P/Invoke declarations and GetProcAddress call. Sysmon Event ID 7: user32.dll loaded by powershell.exe.
- Test 2API Hash Resolution Simulation
Expected signal: PowerShell ScriptBlock Log Event ID 4104: the hash function implementation and the list of API names being hashed. The output shows API-to-hash mappings as adversarial malware would store them.
- Test 3Inspect Binary IAT for Dynamic Resolution Indicators
Expected signal: Sysmon Event ID 1: dumpbin.exe execution with /imports argument on calc.exe. The findstr filter shows LoadLibrary and GetProcAddress imports if present.
- Test 4Create Minimal-Import Executable for Testing
Expected signal: Sysmon Event ID 1: csc.exe compilation (T1027.004 indicator). Sysmon Event ID 1: dynapi.exe execution from Temp. Sysmon Event ID 7: kernel32.dll and user32.dll loaded by dynapi.exe. The dynapi.exe IAT will contain only LoadLibrary and GetProcAddress.
References (5)
- https://attack.mitre.org/techniques/T1027/007/
- https://www.huntress.com/blog/hackers-no-hashing-randomizing-api-hashes-to-evade-cobalt-strike-shellcode-detection
- https://www.blackhat.com/docs/us-15/materials/us-15-Choi-API-Deobfuscator-Resolving-Obfuscated-API-Functions-In-Modern-Packers.pdf
- https://www.ired.team/offensive-security/defense-evasion/windows-api-hashing-in-malware
- https://dr4k0nia.github.io/dotnet/coding/2022/08/10/HInvoke-and-avoiding-PInvoke.html
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