ZoneAlarm is an excellent firewall program, it was quick to download and takes very little resources to run. I have had no problem with program or with anyone infiltrating my PC. It will tell you when a program is probing the PC ports and blocks it instantly.

The programmer writes in assembly code so the program does not require the PC resources that a higher level language would need. (If Microsoft wrote everything they make this way, Windows would be half the size, with less problems).

There is a freeware version and a slightly more advance version for $30 (which I bought after trying the freeware)

Recommended: Yes