Detect DLL side-loading and search-order hijacking (MITRE T1574) where adversaries plant malicious DLLs for legitimate signed applications to load, by analyzing Sysmon Event ID 7 DLL-load events, chec
Imported from mukul975/anthropic-cybersecurity-skills (skills/detecting-dll-sideloading-attacks/SKILL.md). Install upstream with npx skills add mukul975/anthropic-cybersecurity-skills --skill detecting-dll-sideloading-attacks. Copyright stays with the author (Apache-2.0).
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]
Use it
Copy one of these into your project. Installing also returns the manifest and these snippets.
yaml
targets:
- https://api.opensmartroute.ai/api/v1/registry/mukul975-anthropic-cybersecurity-skills-detecting-dll-si-282362/manifest # or paste the manifest below
Manifest
An Open Capability Manifest: the router reads it to know what this does, what it costs and when to pick it.
