Recently, I have setup a website with Arras theme, but since the theme is using the thumbnail management, and heard of security breach, so I decided to install the patch. Below was what I have done.

Patch the theme for timthumb:

1. Download timthumb 
http://timthumb.googlecode.com/svn/trunk/timthumb.php

2. Overwrite the file at /wp-content/themes/arras/library/timthumb.php

Done.

Hope the best as security leakage is not something you should taken lightly.