It's quite normal in a war to build multiple defense lines,
some of which are only capable of stopping a recon team,
while others can stop a armored brigade.
The criteria is that the first kind of line is staffed by
people with a radio, to tell the folks managing the whole
mess that they've encountered the enemy, and in what strength.
In our case, one might do a logical variant: provide a master
password mechanism, and use "not unlocked" as a warning to other
security mechanisms that the owner thinks they're NOT doing
That will definitely catch "probing" attacks, just like a "tripwire"
defense line does.