Tools / Microsoft Threat Modeling Tool (TMT) Interview questions
Explain the internal working of trust boundary crossing detection in TMT?
A trust boundary is rendered on the canvas as a shape with real geometric bounds - a line segment or an enclosing box - just like any other diagram object has a position and size.
At generation time, the engine performs a geometric intersection test between each data flow's path and each trust boundary's geometry, checking whether the flow's line crosses the boundary or has its two endpoints sitting in different trust zones. A positive result sets an internal "crosses trust boundary" flag on that specific flow object, which is exactly the property that boundary-crossing threat rules check for - a flow entirely inside one zone never sets that flag and so never triggers those rules, regardless of what the flow otherwise connects.
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