I would like to make a simple packet filter firewall wich can block specific outbound packets.
I just don't know where to start. I was searching for libraries but all network libraries I found are working on the application layer.
Does anyone of you know a guide on how to start with a project like this?
E: Ok I found out that I will have to use raw sockets, and I've read a quit good guide about how to use them to send your own protocoll headers, but the guide only said it's possible to use them to change outgoing packets, but not how to do that
So if someone has an idea or knows a page with good information on that topic, I would appriciate it