I am new to Modsecurity, trying to use 2.7.5 with nginx 1.4.1 on CentOS 6.4 and i am using the recommended modecurity.conf that was part of the source files.

nginx is setup as a reverse caching proxy to tomcat 7.0.42 and it is setup for SSL using openssl 1.0.1e.

When I enable modsecurity and make a single request for the site nginx is the proxy for, everything seems ok, but when I access the sign in page for the site and enter an incorrect login and password and submit it the system immediately starts to to swap and the CPU load increases.  The site never responds to the request and eventually times out.

When I do the same thing without modsecurity enabled the site immediately returns a failed login attempt.

Any idea why modesecurity would cause something like this?