Block applications with Indicators

The first step is to download the application. I am using Firefox as an example, but you can use any application that provides a certificate.

Navigate to the executable file

1. To extract the certificate from the executable; locate the Firefox file and open its properties.

Extract certificate - Step one

1. Select "Digital signature".
2. Then select the certificate. If there are several, it is not necessary to extract them all.
   
3. Then click on "Details".
   

View Certificate - Step two

1. Click on "View Certificate".

View Certificate - Step three

1. Select "Details".
   
2. Click on "Copy to File".

Certificate Export wizard - Step four

1. Click on "Next".

^{_{Certificate Export wizard - Step Vijf}}

1. Make sure the option "DER encoded binary X.509 (.CER)" is selected.
   
2. Then click on "Next".

Certificate Export wizard - Step Six

1. Click on "Browse" to safe the certificate to the local machine.
2. Then click on "Next".

Certificate Export wizard - Step Seven

1. Click on "Finish" to safe the certificate to the local machine.

^{Navigate to the location to create the policy - Step Eight}
Microsoft has announced that "SecurityCenter" is going to disappear; for that reason I show you, that the best way to create the policy is in the new "security" portal.

1. Navigate to the following location "MDATP Settings - Microsoft 365 security".
2. These are the steps to navigate to it.
   
   1. In the bottom left corner select "Settings".
   2. Then select "Endpoints".
   3. Then select "Indicators".
   4. Then select "Certificates".
3. To add the certificate press "Add item".
   

Create Indicator to block Firefox - Step Nine
Indicator Details

1. Click on "Choose File".
2. Navigate to the location where you saved the .CER file.
   
3. Then click on "Next".

Create Indicator to block Firefox - Step Ten
Response Action

1. Click on "Block" to ensure that Firefox is seen as an unwanted application.
2. Give the policy a name; this is required.
   
3. Give the Policy a description; this is required.

^{Create indicator to block Firefox - Step eleven}
Attention: This is an important choice. My advice is always to test new policies on a select number of devices first. So create a devices group with some test devices. I choose "all devices" since this is not a production environment but my test environment.

1. So choose "select from list" here to not apply this policy to all devices immediately.
2. Then click on "Next".

Below is the link to a Microsoft document how to create a device group.

• Create and manage device groups in Microsoft Defender ATP - Windows security

^{Create indicator to block Firefox - Step twelve}

1. Click on "Save"

^{Create indicator to block Firefox - Step thirteen}
This is all to create the policy. The following points are to consider.

1. The time duration before this policy is active is three hours and sometimes even longer.
2. Below is a demo video how quickly Windows Defender for Endpoint detects the download of Firefox. Should the user install the application anyway it will still be detected and uninstalled later, the user may then be prompted for a restart.
   

^{Create indicator to block Firefox - Step fourteen}
Under incidents, it indicates that there was a device that tried to install Firefox.

1. Navigate to the following location "MDATP Settings - Microsoft 365 security".
2. Under the section "incidents & alerts" you can view the incident