Over all we know everything can be hacked, but there is different levels of effort and knowledge needed to be able to do so. Some hacks are near imposable while others are easy. But how do you classify if it's realistic for someone to be able to compromise a system based off theoretical ideas/hacks? Like some devices had known vulns, or easy ways to get in. While others are very secure, and have no known(yet) vulns.

Example. Hacking an IDS system, then forcing it to send traffic back through it's monitoring ports (which have multiple security protocols to prevent that) Through a span port that is supposed to be one way and into a secure network. While yes, that may be possible the amount of effort and knowledge to do so would be insane.

So how would you guys say that the risk for that does not raise to the level of a real concern?