Many new Flight Simulator add-on products connect to Flight Simulator X (FSX) via the new SimConnect Application Programming Interface (API). When you run FSX with an add-on installed, some non-Microsoft firewall and antivirus applications (such as ZoneAlarm) may detect that FSX is attempting to make a network connection and display a dialog asking you to allow or block this connection.
This "network connection" is necessary for the add-on to connect with FSX. It's a local connection between the add-on and FSX (via a network localhost/127.0.0.1 connection), and does not involve a connection to the Internet. Be assured: FSX is not trying to send personal data about you through the Internet.
Note that Microsoft Windows Firewall will not exhibit this behavior. It will, however, alert you if an add-on is actually trying to access the Internet.
In order for your FSX add-on to work properly with FSX you MUST allow this connection to be made. If you do not allow the connection to be made, the add-on you are trying to run (and all subsequent add-ons that connect to FSX through the SimConnect API) will not work properly.
Some non-Microsoft firewall and antivirus applications will block this "localhost" connection between an add-on and FSX automatically, without any notification. In this case, you must configure the firewall or antivirus application to include both FSX and the add-on (specifically, the fsx.exe file and the addon's .exe file, if it has one) in the list of "trusted exceptions." If this is not done, the add-on will not work properly with FSX. Please refer to the documentation for your specific firewall or antivirus application for details on how to add programs to the list of trusted exceptions.
Please DO NOT uninstall your firewall or anti-virus program!
The purpose of these firewall and antivirus applications is to protect your PC from malicious programs. FSX is not malicious, and should therefore be allowed to make connections with the add-ons you are using.