Edit the firewall policy associated with the clients to add a corresponding rule as follows:

• Open the Symantec Endpoint Protection Manager (SEPM), click the Policies tab, and edit the Firewall Policy you wish to change
• Click on  "Rules" under the "Windows Settings"
• Click on "Add Blank Rule"
• Double-click or right-click>Edit the “Host” field, add a specific IP address so the “Source/Destination” IP is the address you wish to block, (Local/Remote is less generic, and requires the local address of the client on which the rule should be applied)

• Double-click or right-click>Edit the “Action” field and change it from "Allow" to "Block"

• Save and deploy the Firewall Policy as needed.

This will block all incoming and outgoing traffic associated with the specified IP address.

Note: You can also click on Add Rule and accordingly follow the procedure to make a Rule.

Creating a firewall policy