Almost all Intrusion Detection and Prevention Systems (IDS/IPS) can be bypassed. No matter it is commercial or open source, they can be bypassed by any skilled attacker. I am running my home brewed Intrusion Prevention System for over 2 years. It becomes mature and I decided to carry out a bypass test against it.
My plan is to conduct the Application Layer (Layer 7) exploitation behind my IPS. Normally, almost all attacks are from the external. However, I am trying to do it from internal to external.