What is Portscanning?

The act of systematically scanning a computer's ports. Since a port is a place where information goes into and out of a computer, port scanning identifies open doors to a computer. Port scanning has legitimate uses in managing networks, but port scanning also can be malicious in nature if someone is looking for a weakened access point to break into your computer.

Types of port scans:
- vanilla: the scanner attempts to connect to all 65,535 ports

- strobe: a more focused scan looking only for known services to exploit

- fragmented packets: the scanner sends packet fragments that get through simple packet filters in a firewall

- UDP: the scanner looks for open UDP ports

- sweep: the scanner connects to the same port on more than one machine

- FTP bounce: the scanner goes through an FTP server in order to disguise the source of the scan

- stealth scan: the scanner blocks the scanned computer from recording the port scan activities.

Port scanning in and of itself is not a crime. There is no way to stop someone from port scanning your computer while you are on the Internet because accessing an Internet server opens a port, which opens a door to your computer. There are, however, software products that can stop a port scanner from doing any damage to your system.