Birp
Overview:
BIRP is a tool that will assist in the security assessment of mainframe applications served over TN3270. Much like what BURP and other web application proxies do for web application assessments, BIRP aims to do the same for TN3270 application assessments. And, much like with web applications, being able to see and modify fields that the application developer assumed were neither visible nor modifiable allows security assumptions be bypassed.
In particular, BIRP provides two capabilities for the aspiring TN3270 hacker. The first is that it shows all the data returned by the application in the screen. This includes hidden fields. The second is that it allows fields marked as "protected" aka "non modifiable" to be modified. Depending on how the application has been developed, this can allow application functionality to be modified.