Airscanner Mobile Firewall for Windows Mobile Pocket PC is a low-level, bi-directional, packet filtering firewall that examines all incoming and outgoing TCP/IP traffic. This personal firewall ensures that data is permitted based on access control lists that you select from a set of predefined filters, or from filters that you create yourself. The firewall parses packets as they come in (or go out) on the wire or over the air, and it matches the data against a rule set of ports and IP addresses, URLs, etc.
Unlike some other products, Airscanner Mobile Firewall is not a simple port blocker or application port monitor. It is a true, full strength packet filtering application.