Which IDP action is also referred to as a silent discard?

The correct answer is D. drop packet. In IDP terminology, a silent discard means the offending packet is discarded without sending reset packets or other connection-closing signals back to the endpoints. Juniper defines the Drop Packet IDP action as dropping a matching packet before it reaches its destination while not closing the connection. That is the closest and correct IDP action for “silent discard” in the listed choices.

Option A, no action, is wrong because it does not discard anything; Juniper describes No Action as taking no enforcement action, typically used when the administrator only wants logging. Option B, close client and server, is wrong because that action actively closes the session by sending TCP RST packets to both sides, which is explicitly not silent. Option C, ignore connection, is wrong because it stops further IDP scanning for the rest of the connection; it does not discard the packet. Juniper distinguishes these actions clearly: drop packet discards the offending packet, drop connection blocks the whole connection, and close actions send reset packets. Reference topics: IDP actions, drop packet, close client and server, ignore connection, silent discard behavior.