What can other people on my network see

[thedamndest]

And can I see what other people are doing? I am assuming if I am on an open network only the administrator can see what (porn) websites I am visiting, but I don't know if that's correct. If I go to a Wi-Fi hotspot can anyone on the network check me out and vice versa? If so, can I prevent this from happening somehow?

[Xero]

If your PC is actively sharing any folders they'll be able to see those folders and, if they're not password protected, their contents.

If you mean your activity, if it's not over a secure connection (IE: https) then anyone who is purposefully searching it out can see all your traffic, including anything put into forms (passwords, etc). It can't just be stumbled upon by accident.

[thedamndest]

I don't believe I am sharing any folders. Or maybe I am. What is the default?

Tell me more about this activity monitoring? How easy is it to find everything you have mentioned?

[Xero]

The default isn't to share any but the "shared" folders, and even then you have to enable sharing.

Really, I only have a general idea of how it's done. Basically someone can pick up anything you're doing with specific software and possibly hardware. It's probably not hard to find if you know what you're doing, but anyone who's going to use this kind of technology obviously knows where to get it.

Read this:
http://wireless.gumph.org/content/6/3/081-public-wifi-safety.html