A type of mission where a CHERUB agent tries to breach the security of a government installation, such as an airport, or a building that is a likely terrorist target. CHERUB agents are usually required to either break into a building, or smuggle an article such as a gun or explosives through a security checkpoint. Children are useful on these missions because security staff tend not to suspect them.

Security checks are rarely dangerous, apart from the occasional dog bite or sprained limb. These missions are often given to newly qualified agents before they are allowed to go on more dangerous or complicated missions.