Ask all you like. If there's something I don't want to answer, I'll let you know, but I've been here too long to be offended by curiosity.

*The idea prompts a brief, wry smile.*

I've seen a few measures, fairly successful. Setting up defenses on the home side of the portal proves quite effective, as anything stepping through is leaving the protection of the AV field. Some soldiers from one world have even set up sort of a border checkpoint on the Nexus side of their door, and warded it with various spells as well. Ask Stratos Caelus about it, he's in charge there.