The JBoss AS 6.0 Security Guide includes an example of password hashing:

http://docs.jboss.org/jbosssecurity/docs/6.0/security_guide/html_single/#= [Open URL]
Using_JBoss_Login_Modules-Password_Hashing

Which uses unsalted MD5. This is an insecure hashing algorithm, vulnerable to known flaws. Please replace the example with a secure hashing algorithm, e.g. salted SHA-256.