I have installed ZoneAlarm Free Firewall on my PC. I removed Anti-Pishing, because this might interfere with my anti-virus program.
I also deactivated the Firefox ExtensionZoneAlarm Security Engine 1.5.350.0, because I don't know whether it does still make sense and it might worden the performance(?).
Now I see that there is a Firefox Plugin named npFFApi and I don't know where it does come from. Maybe it is connected with the ZA Firewall installation?

I would be glad if anybody could give me an answer.