Information, Computer and Network Security Terms Glossary and
Port Scan Attack
Port Scan attack refers to scan TCP/UDP ports to discover services they can break into. All machines connected to a LAN or connected to Internet via a modem run many services that listen at well-known and not so well-known ports. By port scanning the attacker finds which ports are available (i.e., being listened to by a service). Essentially, a port scan consists of sending a message to each port, one at a time. The kind of response received indicates whether the port is used and can therefore be probed further for weakness.
Firewall, TCP ports, UDP ports, PSAD