I have no idea if my internet is being leached but I just thought of it. I'm a n00b at networking, so I probably have my internet protected from wireless seekers but just in case how can I check to make sure? Thanks.
to add to what fischju said, if you dont need wifi, turn it off. if you want it... enable WPA2 (which should enalbe AES encryption, NOT TKIP) (you may need a patch for XP to use SP2 found here: https://www.microsoft.com/downloads/details.aspx?familyid=662BB74D-E7C1-48D6-95EE-1459234F4483&displaylang=en use a strong passphrase for WPA2 consisting of upper case, lower case, numbers and a symbol or 2. this will make it much harder for a potential intruder to guess or crack it (and make it at least 8 characters long). turn on MAC filtering, this way only the MAC addresses you want are allowed to connect to your wifi (such as your PC's wireless NIC's MAC address). disable SSID broadcasting (you can still connect to your wifi, you just wont see it in the list of available Access Points). turn of DHCP on your router/ AP and statically set all your IP addresses (in the range of 192.168.1.x for the IP, 255.255.255.0 for the subnet, and whatever your default gateway is (usually 192.168.1.1) and your DNS servers (provided by your ISP). if you do want DHCP, then just limit the number of DHCP addresses to be given out to a low number. specifics on each of these steps will vary depending on your wifi router/access point depending on your router/ap you should also be able to see a list of MAC addresses (hosts) that are connected and using the connection. if you see any that arent yours, then you may have a problem.