Certutil.exe may download a file from a remote destination using
-VerifyCtl. This behavior does require a URL to be passed on the command-line. In addition,
-f (force) and
-split (Split embedded ASN.1 elements, and save to files) will be used. It is not entirely common for
certutil.exe to contact public IP space. \ During triage, capture any files on disk and review. Review the reputation of the remote IP or domain in question. Using
-VerifyCtl, the file will either be written to the current working directory or
- Type: TTP
Product: Splunk Behavioral Analytics
- Last Updated: 2022-02-16
- Author: Michael Haag, Splunk
- ID: 9ac29c40-8f6b-11ec-b19a-acde48001122
Kill Chain Phase
- Command and Control
- CIS 10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 $main = from source | eval timestamp = time | eval metadata_uid = metadata.uid | eval process_pid = process.pid | eval process_file = process.file | eval process_file_path = process_file.path | eval process_file_name = lower(process_file.name) | eval process_cmd_line = process.cmd_line | eval actor_user = actor.user | eval actor_user_name = actor_user.name | eval actor_process = actor.process | eval actor_process_pid = actor_process.pid | eval actor_process_file = actor_process.file | eval actor_process_file_path = actor_process_file.path | eval actor_process_file_name = actor_process_file.name | eval device_hostname = device.hostname | where (process_file_name="certutil.exe" AND process_cmd_line LIKE "%split%" AND process_cmd_line LIKE "%verifyctl%") OR process_cmd_line LIKE "%verifyctl%" --finding_report--
The SPL above uses the following Macros:
windows_certutil_verifyctl_download_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 successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the
Endpoint datamodel in the
Known False Positives
Limited false positives in most environments, however tune as needed based on parent-child relationship or network connection.
Associated Analytic Story
|90.0||90||100||An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest_device_id$ by user $dest_user_id$ attempting to download a file.|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
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