Welcome to the forum!
You have neighbors that use X10? I've never had anyone near me that uses X10.
That said, you can't detect "alien" commands as you put it. The only way to eliminate them would be some sort of whole house filter and that would only block power line signals.
If you do have a neighbor using X10 your best bet would be to make friends and divide up the
HCs. Keep in mind unless you live in an appartment, them odds of a signal reaching you are very slim unless they live right next to you.
Garage doors come with remotes that provide 1,000,000s of possible codes for security many even have rotating codes. Keep in mind if you use an X10 module to open your garage you have reduced that security to only 256 possible codes. I would never allow X10 to open my garage. I do, however, allow X10 to close my garage automatically.