An open-source Firefox extension called Firesheep has shined a spotlight on just how insecure it is to use unprotected WiFi networks.

It's widely known that unprotected WiFi networks make sensitive data readily available for anyone with the technical skill necessary to find it, as demonstrated by Google's four-year Street View WiFi data gathering odyssey.

Google got into trouble for being unaware that software in its Street View cars was vacuuming data, but those broadcasting sensitive information over their networks and those running Web services with inadequate security somehow escaped blame.

That may change, thanks to Firesheep, which allows anyone to scan unprotected WiFi networks for users who are logged into Facebook, Twitter, Google, Amazon, and a variety of other Web 2.0 services and to impersonate those users by hijacking their session cookie.

"On an open wireless network, cookies are basically shouted through the air, making these attacks extremely easy," wrote Firesheep creator Eric Butler in a blog post. "This is a widely known problem that has been talked about to death, yet very popular Web sites continue to fail at protecting their users. The only effective fix for this problem is full end-to-end encryption, known on the Web as HTTPS or SSL."

Butler says that Web sites have a responsibility to protect their users and that he hopes Firesheep will encourage Web sites to take action.

The Electronic Frontier Foundation is urging Firefox users to employ an extension called HTTPS Everywhere to counter the threat. At its name suggests, HTTPS Everywhere tries to force every connection to use HTTPS encryption, though it only works if the Web site in question has implemented HTTPS.

"Firesheep makes loud and clear something that EFF has said for some time: major Web sites need to implement HTTPS properly and completely," wrote the EFF's Seth Schoen and Richard Esguerra in a blog post.

Another alternative is a Firefox extension called Force-TLS. Using a VPN also works.

As perimeters melt away, security goes beyond encryption, authentication, and monitoring. We also need to ensure privileged users aren't betraying trust. In this report, we'll cover ways to track who did what to which system, and when. Download the report here (registration required).