Detection: Windows CertUtil VerifyCtl Download

Description

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 %APPDATA%\..\LocalLow\Microsoft\CryptnetUrlCache\Content\<hash>.

Annotations

No annotations available.

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
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References


Version: 4