Securing Your Drupal Module - Part 1 - buildamodule.com

Security is not usually not a primary concern for a Drupal developer when they build their first module. That makes sense because there's a lot to learn. But Drupal gives you some real incentives to implement basic security techniques by making sure that when you make your module secure, you also make your life a whole lot easier. Also, knowing you're responsible for gaping security holes on someone else's site is a burden to the conscientious coder. Save yourself the pain and spend an hour now learning the basics. In this first part of a 4-part series on securing your module, I'll help define the main security concerns you're likely to face, and introduce you to a small family of functions that will guard against 99% of the attacks on your code. This series was inspired by the excellent book "Cracking Drupal" by Greg Knaddison. When you have the time, I'd highly suggest picking up a copy and reading it front to back.