Detect Netsh Helper DLL in CrowdStrike LogScale
Adversaries may establish persistence by executing malicious content triggered by Netsh commands. Netsh.exe (also referred to as network shell) is a Windows command-line scripting utility that interacts with the network configuration of a system. Netsh contains functionality to add helper DLLs for extending functionality of the built-in tool. The paths to registered netsh helper DLLs are entered into the Windows Registry at HKLM\SOFTWARE\Microsoft\NetSh. Adversaries can use netsh.exe helper DLLs to trigger execution of arbitrary code in a trusted process (netsh.exe) whenever netsh.exe is executed, which may also provide privilege escalation if netsh.exe runs elevated.
MITRE ATT&CK
- Tactic
- Privilege Escalation Persistence
- Technique
- T1546 Event Triggered Execution
- Sub-technique
- T1546.007 Netsh Helper DLL
- Canonical reference
- https://attack.mitre.org/techniques/T1546/007/
LogScale Detection Query
// Detect suspicious NetSh registry key modifications (non-system DLL)
#repo=base_sensor
(
(#event_simpleName=RegSetValue OR #event_simpleName=RegCreateKey)
| TargetObject = /SOFTWARE\\Microsoft\\NetSh/i
| RegStringValue != /(?i)(windows\\system32|syswow64)/
| DetectionType := "NETSH_SUSPICIOUS_DLL_REGISTERED"
)
OR
(
#event_simpleName=ProcessRollup2
| ImageFileName = /\\netsh\.exe$/i
| DetectionType := "NETSH_EXECUTED"
)
| groupBy(
[ComputerName, UserName, DetectionType, TargetObject, RegStringValue, ImageFileName, CommandLine],
function=[
count(aid, as=EventCount),
min(@timestamp, as=FirstSeen),
max(@timestamp, as=LastSeen)
]
)
| sort(LastSeen, order=desc)Detects Netsh Helper DLL persistence (T1546.007) in CrowdStrike Falcon using LogScale CQL by monitoring RegSetValue and RegCreateKey events targeting SOFTWARE\Microsoft\NetSh with non-system DLL paths, and ProcessRollup2 events for netsh.exe execution. Groups results by host and user for analyst review.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate network configuration software bundled with enterprise applications (e.g., Cisco, Juniper network clients) may register helper DLLs in vendor-specific directories during installation
- Group Policy-driven network settings pushed via GPMC may invoke netsh.exe frequently on domain-joined endpoints, generating high-volume process execution alerts
- Security scanning tools that enumerate netsh helper DLLs as part of system auditing or vulnerability assessment workflows may trigger registry read-adjacent events
Other platforms for T1546.007
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 1Register Malicious Helper DLL in NetSh Registry
Expected signal: Sysmon Event ID 13 (Registry Value Set): TargetObject=HKLM\SOFTWARE\Microsoft\NetSh\ArgusTestHelper, Details=C:\Users\Public\argus_helper.dll. Security Event ID 4657 if registry auditing enabled. Process creation for reg.exe with add arguments.
- Test 2Register Helper via netsh Command
Expected signal: Process creation for netsh.exe with 'add helper' arguments. Sysmon Event ID 13 for the resulting registry modification to HKLM\SOFTWARE\Microsoft\NetSh. The netsh.exe itself making the registry change is a valid detection path.
- Test 3Create and Register Functional Helper DLL
Expected signal: Process creation for powershell.exe using Add-Type. File creation event for netsh_test_helper.dll in Public folder. Sysmon Event ID 13 for NetSh registry key modification. The DLL in a user-writable path (Public) registered in NetSh is the highest-confidence indicator.
References (4)
- https://attack.mitre.org/techniques/T1546/007/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1546.007/T1546.007.md
- https://www.fireeye.com/blog/threat-research/2017/05/fin7-shim-databases-persistence.html
- https://docs.microsoft.com/en-us/windows-server/networking/technologies/netsh/netsh-contexts
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