Detect Digital Certificates in Microsoft Sentinel
Adversaries may buy and/or steal SSL/TLS certificates that can be used during targeting. SSL/TLS certificates are designed to instill trust. They include information about the key, information about its owner's identity, and the digital signature of an entity that has verified the certificate's contents are correct. Adversaries may purchase or steal SSL/TLS certificates to further their operations, such as encrypting C2 traffic or enabling Adversary-in-the-Middle attacks if the certificate is trusted or added to the root of trust. Free certificate authorities (e.g., Let's Encrypt) enable adversaries to acquire certificates at no cost. Compromised certificate authority infrastructure (e.g., DigiNotar) allows issuance of fraudulent certificates for any domain. After obtaining a digital certificate, an adversary may install it on infrastructure under their control to legitimize malicious communications.
MITRE ATT&CK
- Tactic
- Resource Development
- Technique
- T1588 Obtain Capabilities
- Sub-technique
- T1588.004 Digital Certificates
- Canonical reference
- https://attack.mitre.org/techniques/T1588/004/
KQL Detection Query
// Detection: Unauthorized certificate installation in Windows certificate trust stores
// Monitors registry paths for additions to Trusted Root CA and Intermediate CA stores
// by unexpected processes outside of known software deployment tooling
DeviceRegistryEvents
| where Timestamp > ago(24h)
| where RegistryKey has_any (
"SOFTWARE\\Microsoft\\SystemCertificates\\Root\\Certificates",
"SOFTWARE\\Microsoft\\SystemCertificates\\CA\\Certificates",
"SOFTWARE\\Policies\\Microsoft\\SystemCertificates\\Root\\Certificates",
"SOFTWARE\\Policies\\Microsoft\\SystemCertificates\\CA"
)
| where ActionType in ("RegistryValueSet", "RegistryKeyCreated")
| where InitiatingProcessFileName !in~ (
"svchost.exe", "lsass.exe", "wuauclt.exe", "TrustedInstaller.exe",
"MicrosoftEdgeUpdate.exe", "MsMpEng.exe", "SgrmBroker.exe"
)
| extend CertStoreType = case(
RegistryKey has "Root\\", "Trusted Root CA",
RegistryKey has "CA\\", "Intermediate CA",
"Other"
)
| extend CertThumbprint = tostring(split(RegistryKey, "\\")[-1])
| project
Timestamp,
DeviceName,
AccountName,
ActionType,
CertStoreType,
CertThumbprint,
RegistryKey,
InitiatingProcessFileName,
InitiatingProcessCommandLine,
InitiatingProcessParentFileName
| sort by Timestamp descDetects unauthorized modifications to the Windows certificate trust store by monitoring registry write events under SystemCertificates and Group Policy certificate paths. Excludes known-legitimate OS and security processes that routinely update certificate stores. Certificate additions to Trusted Root CA or Intermediate CA stores by unexpected processes (PowerShell, cmd.exe, unsigned binaries, or software installers outside change windows) indicate adversary activity: installation of a fraudulently-acquired certificate to enable AiTM attacks, C2 TLS trust establishment, or signed malware execution.
Data Sources
Required Tables
False Positives & Tuning
- Enterprise software deployments pushing corporate root CA certificates via SCCM, Intune, or GPO — msiexec.exe or specific application installers will modify certificate stores during installation
- Browser auto-updates (Chrome, Edge, Firefox) that maintain bundled root certificate programs and refresh them via their update processes
- VPN client software and SSL inspection proxy agents (Zscaler, Netskope, Blue Coat) installing their TLS inspection root certificates during agent deployment
- Security products (EDR agents, DLP tools) that install their own root CAs for local HTTPS inspection during initial endpoint enrollment
Other platforms for T1588.004
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 1Install Self-Signed Root Certificate via certutil
Expected signal: Sysmon Event ID 13 (RegistryValueSet) with TargetObject = HKLM\SOFTWARE\Microsoft\SystemCertificates\Root\Certificates\<thumbprint>. Sysmon Event ID 1 for certutil.exe with CommandLine containing '-addstore Root'. Sysmon Event ID 1 for powershell.exe with CommandLine containing 'New-SelfSignedCertificate' and 'Export-Certificate'. DeviceRegistryEvents (MDE) showing ActionType=RegistryValueSet on the Root certificate store path with InitiatingProcessFileName=certutil.exe.
- Test 2Install Certificate via PowerShell Import-Certificate
Expected signal: Sysmon Event ID 13 (RegistryValueSet) with TargetObject containing Root\Certificates\<thumbprint> and initiating process powershell.exe. PowerShell ScriptBlock Log Event ID 4104 capturing the full script including 'Import-Certificate' targeting 'Cert:\LocalMachine\Root'. Sysmon Event ID 11 (FileCreate) for the temporary .cer file in %TEMP%.
- Test 3Enumerate Certificate Stores for Pre-Attack Reconnaissance
Expected signal: Sysmon Event ID 1 for certutil.exe with CommandLine containing '-store Root' and '-store CA'. Sysmon Event ID 1 for powershell.exe with CommandLine containing 'Get-ChildItem Cert:' and 'HasPrivateKey'. PowerShell ScriptBlock Log Event ID 4104 capturing full certificate enumeration script.
- Test 4Download and Install Certificate from Remote URL via certutil URLCache
Expected signal: Sysmon Event ID 1 for certutil.exe with CommandLine containing '-urlcache -split -f http://'. Sysmon Event ID 3 (NetworkConnection) for certutil.exe connecting to 127.0.0.1:8080 (or external IP in real attacks). DeviceProcessEvents CommandLine field captures the URL attempted. Download attempt generates telemetry regardless of server availability.
References (9)
- https://attack.mitre.org/techniques/T1588/004/
- https://threatpost.com/final-report-diginotar-hack-shows-total-compromise-ca-servers-103112/77170/
- https://www.splunk.com/en_us/blog/security/tall-tales-of-hunting-with-tls-ssl-certificates.html
- https://letsencrypt.org/docs/faq/
- https://crt.sh
- https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/certutil
- https://learn.microsoft.com/en-us/powershell/module/pki/import-certificate
- https://www.recordedfuture.com/research/cobalt-strike-servers
- https://docs.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4104
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