You tell by checking your wireless router's user setup screens (see lietrature which came with router or download full manual from CD or maker's website).
Different routers display users-online in different ways but it should be pretty obvious as you explore the menus.
To deter intruders always enable wireless security.[/quotemsg
Thank you for addressing my question and I do appologize for not responding as quickly as I should have.
I purchased Netgear WNR2000 (whatever that means) my point is, it has multiple security options but I am forced to use WEP
because that is the highest secuity a device in my network is capable.