Someone using my connection for illegal activities?

Hey guys, i have a cable modem for internet connectivity and a netgear router. i usually have my wifi secured but recently have unsecured it because of soo many people at this house wanting to get on the wifi ( I use a mac address access list for security no password) but anyways lately i have been seeing a device connected to my router named: bjjs41 with mac adress :

00:C0:CA:4A: D0:E2
I live in savannah Ga and when i use an oui lookup tool to get the geographic location of the device it shows up in Nimbia Africa WTF!!! How in the hell is someone thousands of miles away connecting to my router unless someone close by is using my network for illegal activities and is spoofing their MAC address to appear to be from somewhere else? The OUI lookup tool i use also identifies the device as an Alfa device (Even more suspicious to me as these are popular with the war driving people)

Is there any way i can find out where exactly this person is? i have been recently experiencing some technical issues with the laptop and alot of lag on the net. i also booted up the laptop yesterday and noticed that all of my saved passwords in things like IE were no longer saved. do you think i should change all my passwords?
I do not have any software firewalls installed on any of my 3 computers other than whats built into windows.

anyone have any input or advice?


oh also i used this oui lookup tool here http://blog.wlancontroller.com/?p=67

First, the MAC address does not provide you with a physical address. The most it provides is the manufacturer's name, which you found is Alpha Network, Incorporated.

MAC filtering is a poor security method. MAC addresses can be sniffed fairly easily and then spoofed.

Use WPA2 if you can, or at least WPA.