Go to Accessibility.
After selecting your General visibility, start the blacklisting process by adding the names of the companies you want to exclude. Choose equals or contains to decide how accurate you want the result to be.
Contains is recommended, but remember to narrow it down to exclude only the company you wish to blacklist. Writing server or soft may blacklist too many options.
When using equals, writing Dunder Mifflin Lmt. would rule out companies that register as Dunder Mifflin Lmt. only. It would not exclude parts or versions of the name, like DM Lmt. or Dunder Mifflin. If you wish to do so, use the contains property.