Detection: Windows CertUtil URLCache Download
Description
Certutil.exe may download a file from a remote destination using -urlcache. 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. However, it is uncommon for certutil.exe to write files to world writeable paths.
During triage, capture any files on disk and review. Review the reputation of the remote IP or domain in question.
Annotations
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Implementation
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 Processes node.
Known False Positives
Limited false positives in most environments, however tune as needed based on parent-child relationship or network connection.
Associated Analytic Story
Risk Based Analytics (RBA)
| Risk Message | Risk Score | Impact | Confidence |
|---|---|---|---|
| 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. | 90 | 90 | 100 |
References
Version: 4