The following analytic utilizes a Windows Event Log - CAPI2 - or CryptoAPI 2, to identify suspicious certificate extraction. Typically, this event log is meant for diagnosing PKI issues, however is a great source to identify certificate exports. Note that this event log is noisy as it captures common PKI requests from many different processes. EventID 70 is generated anytime a certificate is exported. The description for EventID 70 is "Acquire Certificate Private Key". STRT tested this analytic using Mimikatz binary and the implementation of Mimikatz in Cobalt Strike.
- Type: Anomaly
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2023-02-08
- Author: Michael Haag, Splunk
- ID: 905d5692-6d7c-432f-bc7e-a6b4f464d40e
Kill Chain Phase
- CIS 10
1 2 3 4 5 6 7 `capi2_operational` EventCode=70 | xmlkv UserData_Xml | stats count min(_time) as firstTime max(_time) as lastTime by Computer, UserData_Xml | rename Computer as dest | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_steal_authentication_certificates_cryptoapi_filter`
The SPL above uses the following Macros:
windows_steal_authentication_certificates_cryptoapi_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
To implement this analytic, one will need to enable the Microsoft-Windows-CAPI2/Operational log within the Windows Event Log. Note this is a debug log for many purposes, and the analytic only focuses in on EventID 70. Review the following gist for additional enabling information.
Known False Positives
False positives may be present in some instances of legitimate applications requiring to export certificates. Filter as needed.
Associated Analytic Story
|24.0||30||80||Certificates were exported via the CryptoAPI 2 on $dest$.|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
source | version: 1