I don't work at the port level much, but understand that there are usual uses for several... so that monitoring those for suspicious activity could be part of a

I don't work at the port level much, but understand that there are usual uses for several... so that monitoring those for suspicious activity could be part of an overall security strategy. Anyone know of widgets or tiny GUI-based apps for Windows/ OSX / Linux that might periodically monitor (and maybe alert) regarding port activity of greatest concern?