Greetings,
I recently installed the free ZoneAlarm firewall as it was recommended to me by several people. However, after a day or two, it reports that more than 5731 intrusions (and counting) have been blocked since install.

This HAS to be some kind of marketing scam to get you to buy the full product. No other firewall I have had, (BitDefender Internet Security Suite, Comodo, etc) has ever supposedly "blocked" that many intrusions.
Is all this true?