Tamper resistance is resistance to (intentional malfunction or sabotage) by either the normal users of a product, package, or system or others with physical access to it. There are many reasons for employing tamper resistance.
Tamper resistance ranges from simple features like screws with special drives, more complex devices that render themselves inoperable or encrypt all data transmissions between individual chips, or use of materials needing special tools and knowledge. Tamper-resistant devices or features are common on packages to deter package or product tampering.
Anti-tamper devices have one or more components: tamper resistance, tamper detection, tamper response, and tamper evidence. In some applications, devices are only tamper-evident rather than tamper-resistant.
Tampering involves the deliberate altering or adulteration of a product, package, or system. Solutions may involve all phases of product production, packaging, distribution, logistics, sale, and use. No single solution can be considered as "tamper-proof". Often multiple levels of security need to be addressed to reduce the risk of tampering. Some considerations might include:
Tamper means interfere with (something) without authority or so as to cause damage.
Nearly all mains appliances and accessories can only be opened with the use of a screwdriver (or a substitute item such as a nail file or kitchen knife). This prevents children and others who are careless or unaware of the dangers of opening the equipment from doing so and hurting themselves (from electrical shocks, burns or cuts, for example) or damaging the equipment. Sometimes (especially in order to avoid litigation), manufacturers go further and use tamper-resistant screws, which cannot be unfastened with standard equipment. Tamper-resistant screws are also used on electrical fittings in many public buildings primarily to reduce tampering or vandalism that may cause a danger to others.
A user who breaks equipment by modifying it in a way not intended by the manufacturer might deny they did it, in order to claim the warranty or (mainly in the case of PCs) call the helpdesk for help in fixing it. Tamper-evident seals may be enough to deal with this. However, they cannot easily be checked remotely, and many countries have statutory warranty terms that mean manufacturers may still have to service the equipment. Tamper proof screws will stop most casual users from tampering in the first place. In the US, the Magnuson-Moss Warranty Act prevents manufacturers from voiding warranties solely due to tampering. A warranty may be dishonored only if the tampering actually affected the part that has failed, and could have caused the failure.