Certificate IOC Block

This guide will show an administrator how to create a block of a specific application based on certificate association.

Role Requirements

Procedure Scope: Administrators

Required Group Membership: Admin.Security

Handbook Reference

Package: Device Security

Domain: Endpoint Indicator Management

Modifies: Unsanctioned Certificates

Defender for Endpoint Certificate IOC Block

1. Navigate to the Certificates – Microsoft Defender portal, select Add Item.
   
2. Click Chose File and upload the malicious certificate, select Next.
   
3. For the response action, select Block and Remediate. This will block the certificate, along with take automated response against the file if found, such as removing the file depending on how the Microsoft automated response goes. Enter a Title and Description for the block, with the intent of giving future context if the rule is to be reviewed at a later date. Click Next.
   
4. Click Save on the next page after reviewing the IOC. Actions should take effect in less than 4 hours.