Detect DLL Side-Loading in Microsoft Sentinel
Adversaries execute malicious payloads by placing a malicious DLL alongside a legitimate, often digitally-signed, application and then invoking that application. Unlike passive DLL search order hijacking (which waits for a victim to run an application), DLL side-loading is active: the adversary both plants the DLL and triggers the legitimate executable. This allows malicious code to run under the cover of a trusted process signature. Common victim executables include security tools, game clients, and enterprise software (e.g., VMware, Symantec, LogMeIn). Widely used by APT groups including MuddyWater, Mustang Panda/TONESHELL, Cobalt Strike operators, and numerous others.
MITRE ATT&CK
- Canonical reference
- https://attack.mitre.org/techniques/T1574/002/
KQL Detection Query
let SuspiciousLocations = dynamic([
"\\AppData\\", "\\Temp\\", "\\ProgramData\\",
"\\Users\\Public\\", "\\Downloads\\"
]);
DeviceImageLoadEvents
| where Timestamp > ago(24h)
| where Signed == false or SignatureState != "SignedValid"
| where FolderPath has_any (SuspiciousLocations)
| join kind=inner (
DeviceProcessEvents
| where Timestamp > ago(24h)
| where ProcessVersionInfoCompanyName != ""
| where not(FolderPath has_any ("\\AppData\\", "\\Temp\\", "\\ProgramData\\"))
| project DeviceId, ProcessId, FileName, FolderPath, ProcessVersionInfoCompanyName, ProcessVersionInfoProductName
) on DeviceId, $left.InitiatingProcessId == $right.ProcessId
| project Timestamp, DeviceName, AccountName,
LoadedDLL=FileName, DLLPath=FolderPath, SHA256,
LoadingProcess=FileName1, LoadingProcessPath=FolderPath1,
Vendor=ProcessVersionInfoCompanyName1
| sort by Timestamp descDetects DLL side-loading by identifying unsigned or invalidly-signed DLLs loaded from user-writable paths by legitimate vendor-branded processes. The key indicator is a mismatch: a process with a legitimate company name (from PE version info) loading an unsigned or untrusted DLL from a suspicious path. This pattern is characteristic of side-loading where the threat actor copies a legitimate vendor binary to a staging directory alongside a malicious DLL.
Data Sources
Required Tables
False Positives & Tuning
- Electron-based applications (Teams, Slack, VS Code) that bundle their own unsigned DLLs in AppData
- Game launchers that use custom DLLs loaded from game installation directories in Program Files
- Development environments that load debug DLLs from build output directories
- Some enterprise software installers that extract and load DLLs from TEMP during installation
Other platforms for T1574.002
Testing Methodology
Validate this detection against 3 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 1DLL Side-Loading via Renamed Legitimate Binary
Expected signal: Sysmon Event ID 11 (FileCreate): Both csc.exe and clrjit.dll created in same TEMP subdirectory within short timeframe. Sysmon Event ID 7 (ImageLoad): if csc.exe is executed, clrjit.dll would be loaded from the local directory first. DeviceFileEvents shows EXE+DLL creation in same writable path.
- Test 2Abusing VMware Binary for Side-Loading (Simulation)
Expected signal: Sysmon Event ID 11 (FileCreate): DLL created in user-writable TEMP location. DeviceFileEvents captures file creation event with SHA256 hash of the dummy DLL.
- Test 3PowerShell Verification of DLL Search Order
Expected signal: Sysmon Event ID 1 (Process Create): powershell.exe spawned with command enumerating PATH environment variable. PowerShell ScriptBlock Logging Event ID 4104 records the full script. No DLL loading events generated.
References (5)
- https://attack.mitre.org/techniques/T1574/002/
- https://www.fireeye.com/content/dam/fireeye-www/global/en/current-threats/pdfs/rpt-dll-sideloading.pdf
- https://unit42.paloaltonetworks.com/dll-hijacking-techniques/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1574.002/T1574.002.md
- https://news.sophos.com/en-us/2023/05/03/doubled-dll-sideloading-dragon-breath/
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