To celebrate the fifteenth anniversary, Checkpoint Software, the security firm behind the popular ZoneAlarm firewall is offering everyone a free copy of ZoneAlarm Pro 2009. The promotion runs for 24 hours, starting at 09:00 EST (06:00 PDT) today, and includes a one-year license for one PC running Windows XP or Vista.

ZoneAlarm protects computers at the operating system level, preventing malware from sending out your information. Unlike the free version of the software, Zone Alarm Pro adds several features including identity-theft protection (with credit monitoring), anti-Spyware protection, and other privacy features. If the only firewall you are using is the one included with Windows, then you might want take advantage of this offer by signing up here – you'll have to wait for an email with the download link.