Linksys Router 1.42.1

I have an old Linksys router (2002) only WEP not WPA security. I run a MacOX with a wireless Mac book. I don’t think the security on my network is secure. A friends laptop was picking up my network and there was no padlock symbol alongside as there was on the others showing. What router should I buy to stop anyone using my network? Am a novice when it comes to all this! So laymans terms please!!