Networking

X-Forwarded-For and IP Allow-List

What is IP Allow-Listing Typically when you want to access a remote resource (e.g. login to a server) you need to provide credentials. It might be a simple username/password, it could be via SSH keys, it could use Mutual TLS with client-side certificates… doesn’t really matter. One concern is “what happens if the credential is stolen”. IP allow-listing is a way of restricting where you can use that credential from.

Data Loss Prevention (DLP)

Working in Cyber Security I’m frequently reminded that the reason we do all the things we do is, ultimately, to protect the data. After all, apps are there to process data, servers (and clouds) are there to run apps and store data. So the whole of cyber security is there to protect the data. It may be Identity and Access Management (restrict access to data to those people who should have access to it).

It was OK before; why is it broke now?

As I was rebuilding my network I came across a problem. In my basement I had previous run a cable from my core switch around the room to the other side, where I had a small 100baseT switch to handle the equipment on that table. I’d also run another cable across the ceiling to the back of the house, where I had the Powerline network. Everything seemed to be working fine, and it had been doing so for years.

Extending the wireless on my router

3 years ago I replaced OpenWRT with a home grown router. It’s worked pretty well, but I wanted to take advantage of improvements in networking (5Ghz!) and also improve coverage. This kinda became important due to COVID lockdown and Work From Home. My library, where I was working from, had very weak network signal. I needed to do better. So I decided to look at turning off in the inbuilt WiFi and use an external WAP (Wireless Access Point, or just AP).

Firewall Basics

What is a firewall? Think of an office building with a keycard entry system. To get into the building you need to put your card to the reader. If it think you’re authorized then the gate will open and you can enter. Similarly, a number of offices require you to “badge out” as well. This badge/gate system is a simple analogy for a firewall. A network firewall may be considered to be a security gate to separate the network up into “inside” and “outside” and you define rules to allow traffic to pass through the gate.

The three tier network is dead

It’s a fairly common design in enterprise networks; a three tier network architecture, with firewalls between the tiers. Typically these layers are split up with variations of the following names: Presentation Layer (Web) Application Layer (App) Data (or storage) Layer (Data) Typically you may have additional tooling in front of each layer; e.g a load balancer, a web application firewall, data loss protection tools, intrusion detection tools, database activity monitoring…

Monitoring my router with graphs

WARNING: technical content ahead! There’s also a tonne of config files, which make this page look longer than it really is, but hopefully they’ll help other people who want to do similar work. A few months back I replaced my OpenWRT router with a CentOS 7 based one. This machine has been working very well, and handles my Gigabit FIOS traffic without any issues.

Building a home router

WARNING: technical content ahead! There’s also a tonne of config files, which make this page look longer than it really is, but hopefully they’ll help other people who want to do similar work. For many years I’ve been using variations of the Linksys WRT54G. I first switched to this router when freeware ROMs became available; I’ve used DD-WRT, Tomato, OpenWRT and others.