ESA astronaut Alexander Gertz gave a talk* some month ago. About the wifi he said that it is good quality in the central spine of the ISS but the outlying modules have very bad reception. Living in big metal cans seems to have that effect. Nothing about the password though.

* https://www.youtube.com/watch?v=l8tTRgTqLn8 (german)

I'm imagining alien life nearing earth and then deciding to head to the next inhabited planet once they notice the wifi has a password on it much like you or I might drive a little further down the road for free wifi.

Some people are just really paranoid.