has someone hacked into my wi-fi??

[spirovski.b]

Not that I'm defending BT...but WEP security is in the default instruction set for configuration set delivered with the devices. I have seen this also in telco operators all over Eastern Europe. The problem is - they just dont give a rat's ass about the users security.
On the original issue. Nihil is right with his instructions. But unless you are keeping scans of your personal ID's on your computer, the identity theft probably happened somewhere else.

[ArPaNET]

How would I see if someone has had unauthorized access??

in most cases you can look at your logs by simply typing in your routers address into your web browser.

just unplug your modem, and run an ethernet cord from your router to your computer, go to your network connections, and the ip address is your routers address... this will give you your router settings, and your logs!

as far as you catching this person on your own, highly unlikely...

so just change your encryption, scan your computer, and follow nihil's advice and seek legal action/help; because not only is this identity theft but as stated above

making allegations that are "calculated to impair the reputation of someone in the eyes of right thinking individuals" is called "slander"

only in the states we call it "defamation of character"...

good luck from here on out...