Detecting DLL Sideloading Attacks
When to Use
- When investigating potential DLL hijacking in enterprise environments
- After EDR alerts on unsigned DLLs loaded by signed applications
- When hunting for APT persistence using legitimate application wrappers
- During incident response to identify trojanized applications
- When threat intel indicates DLL sideloading campaigns targeting specific software
Prerequisites
- EDR with DLL load monitoring (CrowdStrike, MDE, SentinelOne)
- Sysmon Event ID 7 (Image Loaded) with hash verification
- Application whitelisting or DLL integrity monitoring
- Software inventory of legitimate applications and expected DLL paths
- Code signing verification capabilities
Workflow
- Identify Sideloading Targets: Research known vulnerable applications that load DLLs without full path qualification (LOLBAS, DLL-sideload databases).
- Monitor DLL Load Events: Query Sysmon Event ID 7 for DLL loads where the DLL path differs from the application's expected directory.
- Check DLL Signatures: Flag unsigned or untrusted DLLs loaded by signed executables.
- Detect Path Anomalies: Identify legitimate executables running from unusual locations (Temp, AppData, Public) that may be decoy wrappers.
- Hash Verification: Compare loaded DLL hashes against known-good versions and threat intel feeds.
- Correlate with Process Behavior: Check if the host process exhibits unusual behavior (network connections, child processes) after loading the suspicious DLL.
- Document and Remediate: Report sideloading instances, quarantine malicious DLLs, and update detection rules.
Key Concepts
| Concept | Description |
|---|---|
| T1574.002 | DLL Side-Loading |
| T1574.001 | DLL Search Order Hijacking |
| T1574.006 | Dynamic Linker Hijacking |
| T1574.008 | Path Interception by Search Order Hijacking |
| DLL Search Order | Windows DLL loading priority path |
| Side-Loading | Placing malicious DLL where legitimate app loads it |
| Phantom DLL | DLL that legitimate apps try to load but does not exist |
| DLL Proxying | Malicious DLL forwarding calls to legitimate DLL |
Tools & Systems
| Tool | Purpose |
|---|---|
| Sysmon | Event ID 7 DLL load monitoring |
| CrowdStrike Falcon | DLL load detection with process context |
| Microsoft Defender for Endpoint | DLL load anomaly detection |
| Process Monitor | Real-time DLL load tracing |
| DLL Export Viewer | Verify DLL export functions |
| Sigcheck | Digital signature verification |
| pe-sieve | PE analysis for proxied DLLs |
Common Scenarios
- Legitimate App Wrapper: Adversary copies signed application (e.g., OneDrive updater) to temp folder alongside malicious DLL with same name as expected dependency.
- Phantom DLL Exploitation: Malicious DLL placed in PATH location where legitimate app searches for non-existent DLL.
- DLL Proxy Loading: Malicious version.dll proxies all exports to real version.dll while executing malicious code on DllMain.
- Software Update Hijack: Attacker replaces DLL in update staging directory before legitimate updater loads it.
Output Format
Hunt ID: TH-SIDELOAD-[DATE]-[SEQ]
Technique: T1574.002
Host Application: [Legitimate signed executable]
Sideloaded DLL: [Malicious DLL name and path]
Expected DLL Path: [Where DLL should legitimately be]
DLL Signed: [Yes/No]
App Location: [Expected/Anomalous]
Host: [Hostname]
Risk Level: [Critical/High/Medium/Low]Verification Criteria
Confirm successful execution by validating:
- [ ] All prerequisite tools and access requirements are satisfied
- [ ] Each workflow step completed without errors
- [ ] Output matches expected format and contains expected data
- [ ] No security warnings or misconfigurations detected
- [ ] Results are documented and evidence is preserved for audit
Compliance Framework Mapping
This skill supports compliance evidence collection across multiple frameworks:
- SOC 2: CC7.2 (Anomaly Detection), CC7.3 (Incident Identification)
- ISO 27001: A.12.4 (Logging & Monitoring), A.16.1 (Security Incident Management)
- NIST 800-53: SI-4 (System Monitoring), IR-4 (Incident Handling), RA-5 (Vulnerability Scanning)
- NIST CSF: DE.AE (Anomalies & Events), DE.CM (Continuous Monitoring), DE.DP (Detection Processes)
Claw GRC Tip: When this skill is executed by a registered agent, compliance evidence is automatically captured and mapped to the relevant controls in your active frameworks.
Deploying This Skill with Claw GRC
Agent Execution
Register this skill with your Claw GRC agent for automated execution:
# Install via CLI
npx claw-grc skills add detecting-dll-sideloading-attacks
# Or load dynamically via MCP
grc.load_skill("detecting-dll-sideloading-attacks")Audit Trail Integration
When executed through Claw GRC, every step of this skill generates tamper-evident audit records:
- SHA-256 chain hashing ensures no step can be modified after execution
- Evidence artifacts (configs, scan results, logs) are automatically attached to relevant controls
- Trust score impact — successful execution increases your agent's trust score
Continuous Compliance
Schedule this skill for recurring execution to maintain continuous compliance posture. Claw GRC monitors for drift and alerts when re-execution is needed.