Olhando as buscas que os visitantes do blog usaram para chegar aqui pude ver que mais de uma pessoa pesquisou por algo como “iptables diferença entre -I e -A”. Resolvi então escrever um pequeno tutorial explicando como é o fluxo dos pacotes e o processamento destes pelo iptables.

Ambos comandos adicionam regras no firewall, e a diferença é a ordem em que essas são incluídas:

• -I : Insere regras no topo das já existentes (Insert)
• -A : Adiciona regras abaixo das já existentes (Append)

Isto responderia a pergunta de forma resumida, mas para saber o que isso significa, continue lendo!

Read the rest of this entry »

Hello everyone,

I’ve been away for some reasons (including moving this website to a new hosting company), but now I believe that everything is back to normal again, and I’m starting a project that I believe that will benefit a lot of Linux users, and contributors would be greatly appreciated. It is creating a simple, modular, netfilter based personal firewall for Gnu/Linux workstations. If that interested you, read on!

Read the rest of this entry »

Did you know you can easily insert comments on you iptables rules? That way the comment will show up when you list iptables rules (iptables -L) and it goes a long way in helping to keep your firewall understandable.
Read the rest of this entry »

You might have been told before that you can’t sniff traffic on a switched network, since the network switches only send the packets to the destination host instead of broadcasting them to all ports the way old hubs did. That is partially true. There are, however, methods to “trick” the other hosts into sending data to your computer, and I’m going to describe one of those methods on this article.

Read the rest of this entry »