RoboKiller blocks numbers that are on our Global Blacklist of spam numbers, which is updated daily. When a number on this global blacklist calls you, it will automatically be blocked by RoboKiller. RoboKiller will only block spam numbers which are in our global blacklist of spam numbers, and will not block all callers who aren't in your contacts. 

If you have the Neighborhood Spoof Blocking feature turned on, RoboKiller will also block callers who are not in your contacts that call you from numbers with the same first four digits as your number. So for example, if your number is 123-456-7890, RoboKiller will block caller who call you from number starting with 123-4, who are not in your contacts. This "neighbor spoofing" is a common tactic used by spammers. However, this can be turned off, and we suggest doing so if you get a lot of legitimate calls from people in your area who are not in your contacts. 

Keep in mind, you can add any numbers that are incorrectly blocked by RoboKiller to your "allow" list in the app. You can also add your own numbers or ranges that you want the app to block to the "block" list in your app, and they won't be able to call again.