Correctly blocking SSH traffic originating from a specific network requires matching three precise conditions simultaneously in the from clause: the traffic's source-address must equal the 192.168.10.0/24 network, since the requirement is to block traffic coming from that network rather than traffic destined to it; the protocol must be explicitly set to tcp, since SSH operates exclusively over TCP; and the destination-port must be set to 22, because an inbound SSH connection request is always directed at the well-known SSH listening port 22 on the receiving side, regardless of which ephemeral source port the initiating client happens to use. The first option satisfies all three conditions correctly and pairs them with a discard action, cleanly dropping matching traffic. The second option incorrectly substitutes destination-address for source-address, which would match traffic heading toward that /24 rather than traffic originating from it, inverting the intended match direction. The third option incorrectly uses source-port 22 instead of destination-port 22; since the SSH client's source port is a randomly assigned ephemeral value rather than a fixed 22, this term would almost never match real SSH session-initiation traffic. The fourth option relies on a service ssh match condition, which is not valid syntax within the standard Junos firewall filter grammar for family inet; there is no such application-based keyword available at that hierarchy, making the term invalid regardless of the reject action chosen. Reference topics: Junos Enterprise Switching – Firewall Filters, Matching on Address, Protocol, and Port Conditions.