MacOS – How Insecure is OS X Lion (10.7.5)

The primary concern is that any HTTP communications (and other non-secured communications) could be intercepted, including cookies, which often contain your login information. Note that secure communications (HTTPS) have other methods to keep your information safe, so financial communications are usually safe.

The secondary concern is that your Mac can be directly attaqued by any other computer within a 50 m radius. If your Mac doesn't have its firewall on, then this attack may lead to some file access (through guest account), and some remote control (through Apple Remote Desktop, VNC or more secret system vulnerabilities).

This security risk exists equally whether you are using OS X, Windows, Linux, or any other operating system, and there are no additional risks (nor less) on any platform.

The reason your Proxy will not connect without an active connection is because inherently it encapsulates traffic, pipes it over an insecure connection in a secure fashion, and forwards that traffic to another host which actually makes the request. It is like saying you would like to send a secret letter without using the post service, unfortunately it is the base of how you are communicating.

If you join an insecure network and you dont actually perform any actions, there is no risk, that being said, on a mac you do have programs that may automatically request a connection (mail) and send out credentials or try to visit a URL. This is a fairly small risk, you can always keep them closed until you run your proxy software.

In terms of open ports or shared files and folders, if you are advertising these services and you connect to an insecure network, the thing to stop them is your firewall.