To be classified as a High Security Seal, a seal must have obtained a high security rating per ISO 17712 standard. The ISO 17712 rating provides “uniform procedures for the classification, acceptance, and withdrawal of mechanical freight container seals. It provides a single source of information on mechanical seals which are acceptable for securing freight containers in international commerce.”
Seals that belong to the High Security level are sometimes called "barrier seals". They are made of different metals or metal alloys, meaning they require special tools to be opened, such as bolt cutters or pliers. Cable seals and bolt seals also fall into this category. Designed to deter opportunistic theft of high value goods, they also can often be branded and numbered to improve tamper resistance and provide excellent security for containers.