lets say I have a leech infestation, how can I discover who is leeching on my wireless network?
Lock down your network?
^This.
.
If you want to find out IF you have leeches, I’d log into your router’s front-end to see how many connections are being made to the router.
It’s usually 192.168.0.1 to connect to it, but it varies with manufacturer.
maybe I phrased that wrong - is there a program that will show me if unauthorized people are on my network?
edit- ill try that Door
move away from my street
oh and in backtrack type airodump-ng -c
check for clients mac address, if there is one associated with your router thats not written on any of your wifi devices, youve got your leech…
if you really want to find out you can try arp poisoning, you can even do it in windows with Cain & Abel
you can almost see every site they go to
Answered above, routers usually have a way for you to see how many wireless connections are being made to the router and the names of the PC’s that are connecting. No external program involved except a web browser.
EDIT:
Oh you Sersoft 
<3 Airodump (and associated programs). If there is a network nearby that uses WEP encryption, give me 30 mins and I’ll be in.
As for securing your network.
a) Turn off ESSID broadcasting (This makes your network invisible, you need to manually enter both the name and password to connect). This will not make it completely hidden. There are programs (see: Airodump) that will reveal them if someone is connected to them.
b) Use WPA encryption, WEP - no matter how long - can be cracked within 15 mins.
Ahaha why are you like that, share 
When I go on a trip, I bring the laptop with me, and I become one of those leeches you talk about 
Because I need internets.
Trying to manage a bunch of websites is hard without internet
First I see if the place I am staying at has internet, if not then I look for unsecured networks (One time I came across a 1mb/s unsecured network. Funnily enough, after exactly 1gb the speed dropped to 5kb/s). If there are none, then I begin cracking.
I haven even taken the liberty of generating my own script to produce a list of hex combinations for WPA networks (As I think most people have moved away from plain 'ol words).
Anyway, If you want any other suggestions for securing your network ask away. I’m speaking from the POV of the person trying to gain access, so I can tell you what makes me sad.
I’ll be honest, when I saw the name of this thread I was expecting some kind of army of remote-controlled leeches
Anyway I’ve suspected someone of doing this to me, I’ll try some of these…
if you don’t like passwords and still want your SSiD visible to others (visiting relatives? PSP? Nintendo DS? etc.), simply take note of all your regular device’s MAC addies and set up a Wireless MAC filter so only identified nodes can talk with your router. This way you can avoid passwords and persistent hackers if you live in a large apartment complex.
That’s what i did.
-Kawai Tei-
15 minutes is pretty long for a WEP key, I can do it manually in about 3, unless the signal is poor.
Even though all my neighbors have protection, I have the wep keys for 5 of them, even one WPA key that I figured out using my superior intelligence. (okay, it was just their phone number, but still)
It’s funny that I have the fastest internet connection around and my AP is the only one that’s totally unsecured, and I live on a kinda busy street corner and occasionally get leeched from. If you see sersoft2 listed, you’re getting dangerously close to my house.
A dick thing to do would be to simply disable DHCP, sure you have to enter your IP and DNS manually on every PC you use, but most people who steal wifi aren’t smart enough to figure this out and they will just think the signal is too poor.
My wireless network doesn’t need any WEP or WPA encryption. All I did was to block every MAC adress except the ones I want. And bingo! No one can leech me.
I still could, and just for that I would also add you to your own banlist, asshole. 
You guys all have huge e-peens and everything, but I figure if I change my password whenever I notice someone leeching, they’ll move along to a different network rather than taking the time to crack one that changes passwords every other day. It would be nice if I could monitor that without being plugged into my router, though.
That is 15 mins for collecting data + cracking the key. Usually less. My home network took… uhh… 2 mins to crack.
Use airodump to view connected clients MAC address > Spoof my MAC to one of those. Bingo!
If I include the time it takes me to take my laptop out of my bag and the time it takes for linux to boot up, it takes about 10 minutes.
I made over 150$ by hacking wep keys, it’s nice to have lots of friends who can’t afford paying for internet the normal way.
I just leave my wifi access open to everyone and QoS/PF the shit out of people connected onto it.
McAfee notifies me when an unidentified person accesses the network.