Detect Indicator Removal from Tools in Microsoft Sentinel
Adversaries may remove indicators from tools if they believe their malicious tool was detected, quarantined, or otherwise curtailed. They can modify the tool by removing the indicator and using the updated version that is no longer detected by the target's defensive systems. This includes changing file hashes, removing strings identified by AV signatures, obfuscating known-malicious function names, or repacking detected malware. Cobalt Strike includes a built-in capability to modify Beacon payloads to eliminate known signatures. PowerSploit's Find-AVSignature module helps locate detectable byte sequences. Threat actors including UNC3886, OilRig, Turla, APT3, and Deep Panda have iteratively modified their tools in response to public detections.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1027 Obfuscated Files or Information
- Sub-technique
- T1027.005 Indicator Removal from Tools
- Canonical reference
- https://attack.mitre.org/techniques/T1027/005/
KQL Detection Query
let SigBypassTools = dynamic([
"Find-AVSignature", "AVBypass", "DefeatDefender", "Invoke-AVBypass",
"Confuser", "ConfuserEx", "de4dot", "dnspy", "ILSpy",
"pe-bear", "CFF Explorer", "PE Studio", "pestudio",
"hyperion", "Veil-Evasion", "Shellter"
]);
DeviceProcessEvents
| where Timestamp > ago(24h)
| where ProcessCommandLine has_any (SigBypassTools)
or FileName has_any (SigBypassTools)
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine,
InitiatingProcessFileName, InitiatingProcessCommandLine
| sort by Timestamp desc
| union (
DeviceFileEvents
| where Timestamp > ago(24h)
| where ActionType == "FileModified"
| where FileName endswith ".exe" or FileName endswith ".dll"
| where FolderPath !startswith "C:\\Windows\\"
and FolderPath !startswith "C:\\Program Files\\"
| where InitiatingProcessFileName !in~ ("MpCmdRun.exe", "MsMpEng.exe", "svchost.exe", "TrustedInstaller.exe")
| extend SuspiciousModification = true
| project Timestamp, DeviceName, FolderPath, FileName,
InitiatingProcessFileName, InitiatingProcessCommandLine, SuspiciousModification
)Detects execution of known AV bypass and PE modification tools, and modification of PE files outside standard system directories. Adversaries use tools like Find-AVSignature (PowerSploit), ConfuserEx (.NET obfuscator), Shellter (shellcode injection into legitimate PEs), and de4dot (.NET deobfuscator) to iteratively modify their tools and remove AV-detectable signatures. Also surfaces unexpected PE file modifications in non-system locations.
Data Sources
Required Tables
False Positives & Tuning
- Security researchers and red team members using PE analysis tools (PE Studio, CFF Explorer, dnSpy) for legitimate analysis
- Malware analysts using de4dot or ILSpy for deobfuscation of samples in a lab environment
- Software developers modifying their own compiled executables for debugging or patching
- AV software itself modifying quarantined PE files (should be excluded by InitiatingProcessFileName)
Other platforms for T1027.005
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 1Use PowerSploit Find-AVSignature to Locate Detectable Bytes
Expected signal: Sysmon Event ID 3: Network connection to raw.githubusercontent.com. PowerShell ScriptBlock Log Event ID 4104: Find-AVSignature function definition and invocation. Sysmon Event ID 11: AV_results.txt created in %TEMP%. Multiple AV scanner invocations as it binary-searches the file.
- Test 2Obfuscate .NET Assembly with ConfuserEx
Expected signal: Sysmon Event ID 1: PowerShell with Invoke-WebRequest, Expand-Archive, and Confuser.CLI.exe execution. Sysmon Event ID 3: Network connection to GitHub releases. Sysmon Event ID 11: confuserex.zip and extracted directory.
- Test 3Modify Binary Hash with Hex Editor (Byte Patching)
Expected signal: Sysmon Event ID 2 (File Modification Timestamp): hash_test.exe modified. PowerShell ScriptBlock Log: byte array read/write operations and XOR on specific byte. The two certutil hash outputs will differ, demonstrating hash change.
- Test 4Use Shellter to Inject Shellcode into Legitimate PE
Expected signal: Sysmon Event ID 1: PowerShell process creation. Sysmon Event ID 1: notepad.exe spawned by PowerShell. PowerShell ScriptBlock Log with simulated Shellter workflow description.
References (4)
Unlock Pro Content
Get the full detection package for T1027.005 including response playbook, investigation guide, and atomic red team tests.