A cross-domain solution is a controlled gateway for moving data between separate security domains, such as an isolated OT network and an enterprise or external network. Unlike ordinary routing or a shared file share, it enforces policy on every transfer so only approved data, formats, directions, and users can cross the boundary.
In cyber security, this matters because domain separation reduces the blast radius of compromise, but organizations still need limited data exchange for logs, updates, reporting, and operations. A cross-domain solution helps preserve that separation while preventing unrestricted connectivity. Defenders use it to inspect content, block dangerous file types, and require manual review or one-way transfer where needed. Attackers often target the same boundary because a weak bridge can bypass isolation, expose sensitive systems, or move malware into a protected network. Properly designed and tested, it supports continuity without turning segregation into an all-open back door.