@Smoothrunnings said in I have a couple of questions about snort:
@bmeeks
Is the performance impact not related tot he firewalls hardware? From what I understand Ubiquiti uses snort, and their UDM Pro which is more powerful than their old gen router/firewall which doesn't hurt the performance much. It's definitely not a i5-4570 inside their UDM Pro or 8GB of RAM.
Thanks,
Certainly the underlying hardware has a huge impact on the performance of an IDS/IPS. How Snort or any IDS/IPS impacts performance is also heavily influenced by the mode. When running in IDS mode (detection only, no blocking), the impact is very minimal unless you truly have anemic hardware. And with IDS mode, dropping packets (by the IDS) would be unnoticed. IDS mode is a parallel processing path for the packet stream. So a copy of each packet is inspected while the original packet went straight to the kernel stack.
With IPS mode (intrusion prevention which means detection and blocking), there is a performance penalty. This is particularly true with inline IPS modes because every single packet pulled from the NIC has to be inspected by the IPS engine and then either passed on to the kernel network stack or dropped. The IPS engine literally sits between the NIC and the kernel stack, and every packet must go through the IPS engine (no parallel path of "copied" packets). And in this configuration, any dropped packets (as in the IPS engine could not keep up with the packet line rate) means interrupted network flow and thus a performance penalty.