Detect Invalid Code Signature in Elastic Security
Adversaries may attempt to mimic features of valid code signatures to increase the chance of deceiving a user, analyst, or tool. Code signing provides a level of authenticity on a binary from the developer and a guarantee that the binary has not been tampered with. Adversaries can copy the metadata and signature information from a signed program, then use it as a template for an unsigned program. Files with invalid code signatures will fail digital signature validation checks, but they may appear more legitimate to users and security tools may improperly handle these files. Unlike Code Signing (T1553.002), this activity will not result in a valid signature.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1036 Masquerading
- Sub-technique
- T1036.001 Invalid Code Signature
- Canonical reference
- https://attack.mitre.org/techniques/T1036/001/
Elastic Detection Query
sequence by process.entity_id
[library where process.code_signature.status != "trusted" and
process.code_signature.exists == true and
process.code_signature.status in ("error", "expired", "revoked", "untrusted") and
process.code_signature.subject_name != null and
process.code_signature.subject_name != ""
]
[process where event.type == "start" and
process.code_signature.exists == true and
process.code_signature.status != "trusted" and
process.code_signature.status in ("error", "expired", "revoked", "untrusted") and
not process.name in ("MicrosoftEdgeUpdate.exe", "MsiExec.exe")
]Detects processes and loaded libraries with invalid, expired, revoked, or untrusted code signatures. Mirrors the KQL join between file certificate info and process events, flagging signed-but-invalid binaries that may be impersonating legitimate software.
Data Sources
Required Tables
False Positives & Tuning
- Expired signing certificates on legacy internal tooling or build artifacts not yet re-signed after certificate renewal
- Self-signed development binaries deployed to production endpoints during CI/CD pipeline testing
- Third-party vendor software with revoked certificates that have not yet been updated or patched by the vendor
Other platforms for T1036.001
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 1Sign Binary with Invalid Self-Signed Certificate
Expected signal: Sysmon Event ID 7: ImageLoaded with SignatureStatus=Untrusted and Signature containing 'Microsoft Corporation'. Process creation event for test_signed.exe.
- Test 2Copy Signature Metadata with SigThief
Expected signal: Sysmon Event ID 1: Process creation for PowerShell examining signature metadata. File creation events for both binaries in temp directory.
- Test 3Execute Binary with Expired Certificate (Simulated)
Expected signal: PowerShell ScriptBlock Logging Event ID 4104 showing certificate creation. Sysmon Event ID 1 for PowerShell process.
References (6)
- https://attack.mitre.org/techniques/T1036/001/
- https://threatexpress.com/blogs/2017/metatwin-borrowing-microsoft-metadata-and-digital-signatures-to-hide-binaries/
- https://github.com/secretsquirrel/SigThief
- https://learn.microsoft.com/en-us/sysinternals/downloads/sigcheck
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1036.001/T1036.001.md
- https://posts.specterops.io/code-signing-certificate-cloning-attacks-and-defenses-6f98657fc6ec
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