Sounds like you're talking about IPS/IDS
Many many different types. They're mostly on an enterprise level though. The sort of thing that sits in your core network (IDS) or on your border (IPS) and watches all the traffic and looks for particular signatures.
Most decent firewalls have some sort of IPS protections built in, or you can have a standalone appliance.
It also depends on what sort of traffic you're looking at. Is it a server accessible from the internet, or are you more worried about internal users having a go?