Definition: Port has a dual definition in computers. There are various ports on the computer itself: ports to plug in your mouse, keyboard, USB devices, printer, monitor, etc. The kind of ports that are more relevant to information security however are virtual ports found in TCP/IP. Ports are like channels on your computer. Normal web or HTTP traffic flows on port 80. POP3 email flows on port 110. By blocking or opening these ports into and out of your network you can control what kinds of data can flow through your network.