Tamperproofing
Tamperproofing is a term sometimes used for a methodology used to hinder, deter or detect unauthorised access to a device or circumvention of a security system.
Since any device or system can be foiled by a person with sufficient knowledge, equipment, time, etc., the term "tamperproof" is a misnomer. Tamper resistance and tamper-evident systems and devices are better terminology.
Mechanical
Some devices contain non-standard screws or bolts in an attempt to deter access. Examples are telephone switching cabinets (which have triangular bolt heads that a hex socket fits) and computer hard drives, which usually have a star-shaped head for the screws, known as Torx heads. Drivers for these heads are commonly available from electronics retailers.
Electrical
This style of tamper resistance is most commonly found in burglar alarms. Most trip devices (e.g. pressure pads, passive infrared sensors (motion detectors), door switches) use two signal wires that, depending on configuration, are normally open or normally closed. The sensors sometimes need power, so to simplify cable runs, multi-core cable is used. While 4 cores is normally enough for devices that require power (leaving two spare for those that don't), cable with additional cores can be used. These additional cores can be wired into a special so-called "tamper circuit" in the alarm system.
Tamper circuits are just like any other zone (in that they can be n.o. or n.c.) with the exception that the system monitors them 24 hours. Would-be intruders run the risk of triggering the alarm by attempting to circumvent a given device.
Sensors such as movement detectors, tilt detectors, air-pressure sensors, light sensors, etc., which might be employed in some burglar alarms, might also be used in a bomb to hinder defusing.