[ale] Have I been hacked?

[Mark Wright]

I'll start by saying I don't think so.

I have Ubuntu Hardy running behind a Netopia router.  I turned on the  
VNC server yesterday to play with VNC on my christmas toy ipod  
touch.  Set my router to send port 5900 traffic to the Ubuntu box.

Everything was working fine last night and my co-workers were  
properly impressed by my iPod tricks.  When I get home however I find  
that Ubuntu refuses to recognize my password for sudo, package  
manager or anything else.  I haven't logged off yet.

Has someone hacked my box and changed the password?  Specifically,  
before I reset the password and go on as if nothing happened, how can  
I tell?

Thanks for your thoughts.

Mark