Worries about application access have been floating in the Twitter streams of late. Many have voiced concerns about privacy breaches by applications that log users in to Twitter or access their account.
Turns out, those fears are well founded. The Twitter API can be exploited quite easily and let anyone gain access to your Direct Messages.
Using WordPress to Access Direct Messages
For the sake of simplicity, I'm using WordPress to demonstrate accessing Direct Message information.
The Twitter API allows developers access to lots of neat information. You can send messages, update statuses, and do whatever you so please. Sure, there are some permission settings available for developers (read vs. read/write), but few users read this stuff anyway.
Before we go further, apologies to Shannon Whitley for butchering your WordPress plug-in (Twit Connect) and making an example of it. Whitley has developed a simple plug-in for WordPress that bridges authentication between your blog and Twitter, allowing Twitter users to sign in using their existing credentials. This is similar to the comment structure on Search Engine Watch, which I'm sure many of you have used already.
Once you install the plug-in, 90 percent of the work is done. The first thing you'll need to do is register your application with Twitter, which can be done here. You'll be asked for some basic information and you'll then be giving credentials which you will need to fill out in the Twit Connect settings panel.