There's Glomoss that lights up when magic presence/activity is nearby, which can alert guards that something's going on and contact the security wagemage (to send a spirit for) for an astral look around. Iirc, it dies when it's triggered, though. So it'll need to be replaced regularily. Also random spirits or other astral things just flying past will trigger (and kill) it.
There's Awakened Ivy (Street Magic) which is grown to form walls. Requires some maintenance but it forms an actual astral barrier which, when projecting, can only be destroyed by astral combat. And when a mage does that, the plant rapidly decays, alerting mundanes that there's been a breach.
(I'm almost certain there's a second plant with almost the same function, too... Biofiber or something? AFB at the moment. If I remember, I'll try looking it up tonight.)
There's also the Guardian Vines (Street Magic), though I wouldn't recommend putting them anywhere your own employees would go. Their astral form moves around, though, so maybe you could put it in locked closets or something?
Haven Lily (also Street Magic) creates mana ebbs up to rating 3, severely weakening mages/spirits.
That said. None of these plants are selective. They'll hinder the company's magic security as much as they do enemy mages/spirits. It might be possible to come up with an attuned version of them, though, maybe them ignoring/only targetting a specific type of magic. It's not really RAW, but not too far-fetched neither imho. But this does create a potential security hole too if the magical infiltrators use (or pretend to with Masking) the same type of magic.