[amalcon]

I suppose you could always redirect to 127.0.0.1. Maybe even go for a port that's likely to be open on a statistically random compromised system, like 135 (Windows DCOM, can't close it to localhost without breaking like half the system).

Edit: I just tried this in IE on my Win box; the connection even stayed open for a good long time! Firefox blocked it, though, which is probably good.