Lock bumping became a major security concern when videos showing the technique went viral. Unlike picking, bumping requires minimal skill and can open most standard pin tumbler locks in seconds. Understanding the threat helps you defend against it.
A bump key is a key cut to maximum depth on all cuts (999 cut or similar). When inserted slightly short of full insertion and struck (bumped) with a mallet, the kinetic energy travels through the key to the pins. All pins momentarily bounce to the shear line simultaneously, allowing the cylinder to rotate.
Standard pin tumbler locks — which includes most residential deadbolts — are vulnerable to bumping. The technique requires less than 10 minutes of practice to learn and bump keys can be purchased for under $10. Any standard key blank can be filed into a bump key.
Security pins (spool and serrated) significantly complicate bumping by creating false sets that the simple kinetic bump cannot overcome. Disc detainer locks (Abloy), sidebar mechanisms (Medeco), and electronic locks are essentially immune to bump attacks.
Scratch marks around the keyway, a loose or slightly misaligned cylinder, or strange marks on the face of the lock can indicate an attempted bump attack. If you notice these, call a locksmith to assess the lock's integrity.
Upgrade exterior deadbolts to models with documented bump resistance. Add a door chain or security bar for interior reinforcement. Install a door alarm or smart lock that alerts you to unusual activity. Motion-activated lighting reduces opportunities for undetected attempts.