Detect Code Signing Certificates in Google Chronicle
Adversaries may create self-signed code signing certificates that can be used during targeting. Code signing is the process of digitally signing executables and scripts to confirm the software author and guarantee that the code has not been altered or corrupted. Adversaries leverage self-signed certificates to make malicious payloads appear more trustworthy — security tools and users are more likely to trust a signed binary even when the signing authority is unknown. Threat actors including Daggerfly (macOS malware), PROMETHIUM (StrongPity spyware installers), and Patchwork (BackConfig RAT) have created self-signed certificates impersonating legitimate software vendors to sign malicious payloads. This technique is commonly paired with T1553.002 (Code Signing) to bypass application allowlisting, reduce user suspicion, and evade detection tooling that weights signed binaries as lower risk.
MITRE ATT&CK
- Tactic
- Resource Development
- Technique
- T1587 Develop Capabilities
- Sub-technique
- T1587.002 Code Signing Certificates
- Canonical reference
- https://attack.mitre.org/techniques/T1587/002/
YARA-L Detection Query
rule t1587_002_code_signing_cert_creation {
meta:
author = "Argus Detection Engineering"
description = "Detects T1587.002 - self-signed code signing certificate creation and manipulation via Windows SDK tools, PowerShell PKI cmdlets, OpenSSL, certutil, and signtool"
mitre_attack_tactic = "Resource Development"
mitre_attack_technique = "T1587.002"
severity = "MEDIUM"
priority = "MEDIUM"
events:
$e.metadata.event_type = "PROCESS_LAUNCH"
$e.target.process.command_line != ""
(
// Branch 1: Native SDK tools
re.regex($e.target.process.file.full_path, `(?i)\\(makecert|pvk2pfx)\.exe$`)
// Branch 2: PowerShell certificate cmdlets
or (
re.regex($e.target.process.file.full_path, `(?i)\\(powershell|pwsh)\.exe$`)
and re.regex($e.target.process.command_line, `(?i)(New-SelfSignedCertificate|Export-PfxCertificate|Export-Certificate|X509Certificate2|CertEnroll\.CX509|CertificateRequest|codeSigning|1\.3\.6\.1\.5\.5\.7\.3\.3)`)
)
// Branch 3: OpenSSL code signing cert creation
or (
re.regex($e.target.process.file.full_path, `(?i)\\openssl\.exe$`)
and re.regex($e.target.process.command_line, `(?i)\s(req|x509|pkcs12|genpkey|genrsa)\s`)
and re.regex($e.target.process.command_line, `(?i)(codeSigning|1\.3\.6\.1\.5\.5\.7\.3\.3|extendedKeyUsage|-x509)`)
)
// Branch 4: certutil certificate store manipulation
or (
re.regex($e.target.process.file.full_path, `(?i)\\certutil\.exe$`)
and re.regex($e.target.process.command_line, `(?i)(-addstore|-importpfx|-add)`)
)
// Branch 5: signtool signing
or (
re.regex($e.target.process.file.full_path, `(?i)\\signtool\.exe$`)
and re.regex($e.target.process.command_line, `(?i)\ssign`)
)
)
outcome:
$hostname = $e.principal.hostname
$username = $e.principal.user.userid
$process_path = $e.target.process.file.full_path
$command_line = $e.target.process.command_line
$parent_process = $e.principal.process.file.full_path
$is_suspicious_parent = if(
re.regex($e.principal.process.file.full_path, `(?i)\\(cmd|wscript|mshta|cscript|regsvr32|rundll32|msiexec)\.exe$`),
1, 0
)
$is_temp_path = if(
re.regex($e.target.process.command_line, `(?i)\\(temp|appdata|downloads|public)\\`),
1, 0
)
condition:
$e
}Chronicle YARA-L 2.0 rule detecting T1587.002 certificate creation and manipulation. Covers all five detection branches from the reference detection using UDM process event fields. Enriches outcome with suspicious parent and temp path indicators.
Data Sources
Required Tables
False Positives & Tuning
- Developer workstations with legitimate certificate signing workflows in SDLC pipelines
- Security operations or PKI teams managing enterprise certificate infrastructure
- Automated DevOps or CI/CD systems that build and sign software packages as part of normal release processes
Other platforms for T1587.002
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 1Create Self-Signed Code Signing Certificate via PowerShell
Expected signal: Sysmon Event ID 1: Process Create with Image=powershell.exe, CommandLine containing 'New-SelfSignedCertificate' and the spoofed Subject. PowerShell ScriptBlock Log Event ID 4104 capturing the full cmdlet invocation with parameters. Sysmon Event ID 11: File Create for df00tech-codesign.pfx in %TEMP%. Sysmon Event ID 13: Registry value set in HKCU\SOFTWARE\Microsoft\SystemCertificates\My\Certificates\<thumbprint>.
- Test 2Create Self-Signed Certificate Using OpenSSL with Code Signing EKU
Expected signal: Sysmon Event ID 1: Two Process Create events — openssl.exe with 'req -x509' and 'extendedKeyUsage=codeSigning' arguments, then openssl.exe with 'pkcs12 -export' arguments. Sysmon Event ID 11: File Creates for df00tech-key.pem, df00tech-cert.pem, df00tech-adobe.pfx in %TEMP%.
- Test 3Sign Executable with Self-Signed Certificate Using signtool.exe
Expected signal: Sysmon Event ID 1: Process Create with Image=signtool.exe, CommandLine containing 'sign' and '/f %TEMP%\df00tech-codesign.pfx'. Sysmon Event ID 11: File modification event for df00tech-signed.exe (PE authenticode signature appended). Security Event ID 4688 (if process command line auditing enabled) capturing full signtool invocation.
- Test 4Import Self-Signed Certificate to Trusted Root Store via certutil
Expected signal: Sysmon Event ID 1: Process Create with Image=certutil.exe, CommandLine containing '-addstore' and 'Root'. Sysmon Event ID 13: Registry value set in HKLM\SOFTWARE\Microsoft\SystemCertificates\Root\Certificates\<thumbprint>. Security Event ID 4657 (registry value modification) if object access auditing is enabled for HKLM\SOFTWARE\Microsoft\SystemCertificates.
References (12)
- https://attack.mitre.org/techniques/T1587/002/
- https://en.wikipedia.org/wiki/Code_signing
- https://www.bitdefender.com/blog/labs/strongpity-apt-new-version-of-the-spyware-phone-targeted-victims-in-turkey-and-syria/
- https://unit42.paloaltonetworks.com/patchwork-apt-southeast-asia/
- https://www.welivesecurity.com/en/eset-research/evasive-panda-apt-group-monitoring-tibetans/
- https://learn.microsoft.com/en-us/windows/win32/seccrypto/makecert
- https://learn.microsoft.com/en-us/windows/win32/seccrypto/signtool
- https://learn.microsoft.com/en-us/powershell/module/pki/new-selfsignedcertificate
- https://learn.microsoft.com/en-us/defender-endpoint/advanced-hunting-deviceprocessevents-table
- https://learn.microsoft.com/en-us/defender-endpoint/advanced-hunting-devicefileevents-table
- https://learn.microsoft.com/en-us/defender-endpoint/advanced-hunting-deviceregistryevents-table
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1587.002/T1587.002.md
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