The Syrian Shell is described by its original author as
"a PHP Script that coded to help hackers with there hacking trip . with this script you can so easily hack scripts , inject databases , send spam emails , bypass latest security Updates , collecting information , encrypting and decrypting strings , connecting dealings and more ... in this website . I'll show you the features of this PHP shell , some codes in it and some wonders that you haven't ever seen like it . :)"
Edit Jul 10 2011: I've removed the listing of 39 websites that hosted the scripts Ryan Cleary used to send thousands of emails to people he admires were installed, because one of the incompetent website owners asked nicely:
I kindly request you to remove from your blog any references to my web site or myself as soon as possible. Should those references do not disappear from your website, I will be obliged to take further action and contact your hosting provider (blogger.com).
Hoping we can solve this issue in a prompt manner,