Sandbox
A paddock for untrusted code. If it explodes, the paddock takes it. Production is not a paddock.
A sandbox is a constrained virtual space for running new, untrusted, or untested software so a mess stays inside. Mail gateways, browsers, and malware labs all use the idea.
It is a control, not a personality test. Sandbox-aware malware exists. Still use one for unknown attachments. Do not open the sample on the SOC analyst's everyday laptop 'just to see'.
Fact source: ASD's ACSC glossary.