-<h3><a name="section_1_1_1">Iptables</a></h3>
-<p>Although there is more abstract software to manage firewalls, like <em>ufw</em> on debian-based systems and <em>firewall-cmd</em> on redhat systems, Iptables will help you understand what actually happens during filtering, mangling or routing a package. <a href="https://www.frozentux.net/iptables-tutorial/iptables-tutorial.html">https://www.frozentux.net/iptables-tutorial/iptables-tutorial.html</a> has a structured approach in explaining <u>what happends when a package hits the firewall</u>.
+<h3><a name="section_1_1_1">Netcat</a></h3>
+<p>Simple tool to open or connect to TCP or UDP ports and output data through these channels. Build and test proxies. Powerful for debugging. <u>Cryptcat</u> is a similar tool, but with support for cryptography
+</p>
+<h3><a name="section_1_1_2">Sendip</a></h3>
+<p>Create and send IP, TCP or UDP packages. You are able to edit any value within these packages.
+</p>
+<h3><a name="section_1_1_3">Iptables</a></h3>
+<p>Although there is more abstract software to manage firewalls, like <em>ufw</em> on debian-based systems and <em>firewall-cmd</em> on redhat systems, Iptables will help you understand what actually happens during filtering, mangling or routing a package. <a href="https://www.frozentux.net/iptables-tutorial/iptables-tutorial.html">https://www.frozentux.net/iptables-tutorial/iptables-tutorial.html</a> has a structured approach in explaining <u>what happends when a package hits the firewall</u>. Pay extra attention to Network Address Translation. Here is another nice HOWTO: <a href="https://netfilter.org/documentation/HOWTO/NAT-HOWTO-5.html">https://netfilter.org/documentation/HOWTO/NAT-HOWTO-5.html</a>