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I don't know much about firewalls. I wasn't aware they could alter traffic, for example. What do you mean it can be leveraged for evil? As for organization, I

I don't know much about firewalls. I wasn't aware they could alter traffic, for example. What do you mean it can be leveraged for evil? As for organization, I just dump everything I learn in a markdown file on that topic, then look for structure later. So I would just open a file, call it `firewalls.md` and write that down in there. You can accrete a lot of written knowledge over time this way.

ilc 4y ago
They can be used for all types of stuff. Imagine two companies merging. They both used 10.100.0.0/16. If you were in one of the companies wouldn't it be nice if the other re-ip'd? ... Guess what.. they won't and you don't want to. So you make a box, that turns your ips into 10.101.0.0/16 and theirs into 10.102.0.0/16... and you leave your IPs alone :). Yeah, some things won't work across that bridge. But it'll get you started. Firewalls can do really, really evil stuff. DNS? Yeah, we'll answer ALL dns queries.. Even ones you send to 8.8.8.8, or 1.1.1.1... The BOFH playbook is large, and varied. :)
Damogran6 4y ago
Networking, not just firewalls, is about looking at a packet, opening it up, and either passing it along to the next link in the chain, or making a change to (typically) the header and sending it along. There's a TTL or Time To Live value to make packets eventually die, otherwise, packets could potentially move from router to router forever. So at a minimum, your firewall, or router, rewrites the header to Decrement the TTL by one with every hop. Which spawns a really interesting thought experiment that results in the creation of the traceroute utility.