Given your experience with both mod_security and mod_deflate I was wondering if you had experienced the same conflicts that I have. When I disable mod_deflate, mod_security works great, when I enable mod_deflate I get:

[Mon Dec 10 16:21:28 2007] [error] [client 127.0.0.1] ModSecurity: Warning. Operator EQ match: 0. [id "960903"] [msg "ModSecurity does not support content encodings"] [severity "WARNING"] [hostname "www.testsite.com"] [uri "/test.html"] [unique_id "Le3dBH8AAAIAAErHB-QAAAAB"]

Environment: Jetty 6.1.6, JDK 6, Spring 2.5 Web