Category: Uncategorized

Port Knocking

A few months ago, a friend of mine told me about the concept of port knocking, where you send packets to a server on certain ports to authenticate access to the box. A daemon running on your server detects the…

Fallback IPtables

The hardest part of messing with firewall configs is knowing what is going to lock you out of the firewall itself.  It doesn’t to me very often, but I’ve been doing firewalls for 10 years now.  I was thinking about…

Using an Old Server as a Home Firewall

You can use an old PC as a firewall at home (and at work, I guess). It’s not that hard to do if you have a basic knowledge of Linux, DHCP, and IPtables, but that may be saying a lot.…

Mixed-platform LANs and Spanning Tree

We just an HP C-class blade chassis which included two GbE2c network modules.  These modules are Nortel switches running AlteonOS that connect the blades to the rest of your network.  When I turned these guys up the other day, every…

The Principle of Least Privilege

The Principle of Least Privilege says that users or applications should only have access to the what it needs to access and that access should be as limited as possible.  This idea can be applied to any number of things,…