Basically a 100 year old hack on physical door locks that has been kept secret by the locksmithing community. Locksmiths aren't happy about the disclosure, but don't you think it was the locksmith's obligation and responsibility to inform people and businesses using these locks that they are so easily 'hacked'? Especially since locks can be made that are immune from this type of thing! Yes, we've been deceived!

http://www.crypto.com/masterkey.html