CurrPorts is a free application that shows a list with the actual in use ports and also of the application that is using them.
For each opened port CurrPorts can inform details about the name and complete using route of the process, the hour in which this process began and also the user that created it.
CurrPorts also allows to close TCP non-wished connections, to finalize the process that has opened a port and to keep the information collected in an HTML, XML or other file of text.
In order to mark suspicious TCP or UDP ports, CurrPorts would highlight in pink color the controlled by unknown applications ports.
It is not necessary to install CurrPorts to use it. It is necessary just to copy the EXE file in the wished folder, and to open it. It can also be executed from a diskette or a USB memory.