Pattern DD-E

File lock between domains

From a USB stick to a one-way transfer, with the human decision made explicit rather than assumed.

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Area: Data diodes
Environments: 2
Products used: 2

How it is built

One-way path
Data path
Path that does not exist

Media is carried in, validated in a staging zone, and only then released onward.

Used in these environments

File lock and media transferThis is where people work around the protection when it becomes inconvenient — the design has to assume that.
Replacing an air gapMapping the flows comes before choosing the product — the air gap is upheld by manual work that is rarely counted as cost.

How it works

Media is carried in, read in a staging zone, validated, and only then released onward. The staging zone is the pattern: without it, the file lock is a USB port with a procedure attached.

A staging zone is not a DMZ

A DMZ is reachable from both sides. A staging zone is not reachable from the protected domain at all — validation results move outward, never inward on request.

This is where the protection gets worked around

A file lock that takes fifteen minutes when someone needs a file now is a file lock that gets bypassed by a USB stick and a friendly colleague. The countermeasure is not training. It is making the sanctioned path faster than the unsanctioned one, and designing for the case where it is not.