If you have created an android or iphone application and when it connects to your site you recieve a 403 message this means your application is NOT sending a http useragent with the http request and mod_security is blocking the request.

The best way to fix this is to fix the application

http://android-er.blogspot.co.uk/2013/05/set-user-agent-string-of-webview.html

https://developer.att.com/developer/forward.jsp?passedItemId=2400464

shows how to set a http useragent using android. 

http://www.mphweb.com/en/blog/easily-set-user-agent-uiwebview

shows how to set this using iPhone.