If you want to block certain visitors from your project you can set an IP block in Audience. You do this by opeing up Audience settings and then drag a Geo rule to the audience board. Make sure that IP is selected and then change to IS NOT and then add the IP numbers you want to block (separated by comma) in the input field. Hit save and close Audience settings. Make sure to check your Audience settings by opening up a preview of the project.
For example 126.96.36.199, 188.8.131.52, 184.108.40.206