It just keeps getting better

I have a dilemma (when don't I?). I've been getting what I casually refer to as "sexually harassed" at my job on a daily basis. Not necessarily by one person (though there are a few of those, too), but mostly from drive-by harassers. By this I mean men who leer at me as they walk by my "desk" in the lobby and say something along the lines of, "How you doin', baby?" It looks ridiculous when I type it, but I swear it happens.*

*I realize that I cannot adequately convey the lechery that these guys put into their eyes and voices. Reading it in print, it seems like I'm completely overreacting. However, I know what I feel and it ain't pretty, and it ain't harmless.

So my dilemma is: how do I react to these men, and in a way that won't get me fired? It's not like I can tell them to eat shit and die, which would be my normal response. So far I've been so taken aback by the casual lewdness that I barely have time to scowl and look away, much less say anything in response. The thing that really gets me is that I know these guys know that they're making me uncomfortable; in fact, that's the whole point of it for them. They know (don't they? they must) that I am in a public service position and that as such I must put on a happy face and appear polite and friendly to everyone, and that I'm not smiling and saying hello to them because I want to hook up with them after work.

What do I say? How do I respond? Usually they're gone before I can open my mouth so it's not like I can go off on some diatribe about respecting my authority or anything. My thought as I'm writing this is that there is really nothing I can do - jerks are going to be jerks, and unfortunately as a young-ish, not wholly fugly woman, this type of stuff is going to happen and I'm just going to have to grin and bear it, given the dregs of humanity that pass through the door. *Bastards* But in case any of you faithful readers have some helfpul advice, I'm putting this question out to you.