CrowdStrike: Block Bad Hashes

This guide helps you set up your CrowdStrike device and grant necessary permissions so that you can enable the Block Bad Hashes auto remediation in Workbench.

This guide is the first step of a larger process to enable auto remediations. After completing the steps on this page, you will be instructed to return to the Enable an Auto Remediation in Workbench guide to finish your setup.

How It Works

If our SOC identifies a hash that must be blocked, Workbench completes the action automatically unless it is specifically called out as a "Never block" asset (these hashes must be added as context and then configured in Workbench; see Step 2).

CrowdStrike can only block .exe execution through hash. Any other file type is still able to run.

Endpoints Used

CrowdStrike Falcon IOC Management API

/iocs/.../v1 , sha256

Method	Endpoint	Purpose
GET	/iocs/queries/indicators/v1	Pre-check: find an existing IOC matching the hash
POST	/iocs/entities/indicators/v1	Create a custom IOC for the hash with action prevent, severity high, applied to all hosts (the block)

Revert (unblock): GET /iocs/queries/indicators/v1 to find the IOC ID, then DELETE /iocs/entities/indicators/v1?ids=....

Step 1: Allow Appropriate Permissions in Your EDR Console

1. Make sure you assign all API permissions in the CrowdStrike Falcon Setup for Workbench guide.
2. Within API scopes, enable both read and write permissions for IOC Management for the Expel API client.
3. In Prevention Policies, enable Custom Blocking in the Malware Protection/Execution Blocking for each operating system (Windows, Mac, Linux).

   

   

Step 2: Update Your Context

If you do not want to specify any hashes for a "do not block" list, skip to Step 3.

Working with your Customer Success Manager, add any hashes that should be on the "do not block" list as org context for your environment. You will then be able to select those hashes as "Never block" assets when you enable the auto remediation in Workbench.

If our SOC identifies a hash that must be blocked, any hashes added as "Never block" assets are assigned to you as actions rather than being blocked automatically.

Step 3: Return to the Main Setup Guide

Your CrowdStrike device is now ready for the Block Bad Hashes auto remediation. You should now do one of the following:

• If you do not need to set up any other devices for this auto remediation, you can return to the Enable an Auto Remediation in Workbench guide to finish Step 2 of the process.
• If you need to set up additional devices for this auto remediation, or wish to use this device with multiple auto remediations, be sure to complete those setup guides as well before returning to the Enable an Auto Remediation in Workbench guide to finish Step 2 of the process. Make sure to follow the setup guide that is specific to your auto remediation, as device setup instructions are unique to each auto remediation and device.