Ask the Wi-Fi Guru About "Free Public Wi-Fi"

By Aaron Weiss

August 19, 2010

Our monthly Q&A series offers advice to those seeking help with home or small business WLANs. This month our guru offers some insight to all those "Free Public Wifi" hotspots you see around and provides some advice about how to connect a wired Blu-Ray player to a Wi-Fi network.

Our monthly Q&A series offers advice to those seeking help with home or small business WLANs. This month our guru offers some insight to all those "Free Public Wifi" hotspots you see around and provides some advice about how to connect a wired Blu-Ray player to a Wi-Fi network.

Would you like to ask the guru a question? Write the editor.


If you travel much with your wireless laptop or mobile device and don't have the luxury of a 3G adapter or signal, you're familiar with playing the "Wi-Fi lottery". That is, you look at the list of available Wi-Fi hotspots where you are and hope that you can connect to one of them. If there is a free and public wireless hotspot around, you are a lottery winner. If there is a private, but unsecured, hotspot, well, that's between you and The Ethicist. But if there is a "Free Public Wifi" hotspot, then…wait, what is that one?

It turns out that "Free Public Wifi" is showing up in many places these days--except that it isn't free public Wi-Fi. It is, in fact, what is known as a "viral SSID", one of several that has spread like kudzu around the world (another is "hpsetup").

The story of viral SSID's is an interesting one, and is actually not rooted in malice. Wireless networks can be connected two ways: an "infrastructure" network uses an access point (AP) to associate clients. This is the most common type of wireless network and what you are using whenever you connect to a wireless router. The less common alternative is called an "ad-hoc" network, in which two wireless devices connect directly to each other without a router or AP involved. Ad-hoc configurations aren't very common. But when you are using one, your device acts like an AP, broadcasting its SSID for other clients to connect to.

Some operating systems, like Windows XP, try to do you a favor: When you connect to an AP, they remember it, and in the future automatically try to connect when it appears within range. But if there are no AP's within range, your OS may fallback to ad-hoc mode using one of these "memorized" SSID's.

The scenario looks like this: the first person, whom we'll call Patient Zero, connects to an AP called "Free Public Wifi". Their OS helpfully memorizes this SSID. Later, this person is somewhere else without any AP's in range. Their computer switches to ad-hoc mode and attempts to make a connection using "Free Public Wifi". In ad-hoc mode, their machine advertises for partners by broadcasting this SSID.

Another person in the vicinity--Patient One--happens to be scanning for networks and sees "Free Public Wifi". Ooh! They think, free Wi-Fi! They connect to this AP, without realizing they've actually made an ad-hoc connection to another machine. They cannot actually surf the Internet, so it appears that this connection doesn't work. Patient One gives up in frustration. However, their computer, too, has now remembered "Free Public Wifi" and exhibits the same behavior as Patient Zero's machine at a future date and time.

Multiply this effect by millions of people in millions of places, and millions of machines now unwittingly broadcast as "Free Public Wifi" ad-hoc connections, even though they really aren't, and these connections won't work.

The viral SSID is not inherently malicious, but it can be exploited by hackers. Because so many machines now try to automatically connect to an AP with this name, all a hacker needs to do is setup a bad faith AP using this SSID. Done right, this AP could supply working Internet access to computers which automatically connect; but what the users don't know is that the AP is logging and parsing activity, looking for things like clear passwords. Or, in some cases, injecting malware exploits into connected machines (if they are unpatched).

A good defense against viral SSID's is to remove any that are listed in your machine's "preferred wireless networks" -- exact details vary (XP, Vista/7, OS X).

With all that said, it looks like we have just enough time left to squeeze in a reader question.

How can I use my Wi-Fi network with my wired Blu-Ray player?

Q: I have a Blu-Ray player that has LAN ports for an Internet connection. My Wi-Fi router is on the second floor of my house and it would be a big hassle to run a line down to the player. Is there anything that I can plug into the player port so that it can use the Wi-Fi signal? - Daniel

A: You actually have several options, some pricier than others. Presumably both your router and DVD player are near power outlets (otherwise it would be a miracle that they work at all). There are a number of products on the market that can use your existing home wiring to transmit data (without interfering with the electricity). Basically you plug a doohickey into the power outlet near your router, along with an Ethernet cable from that router's LAN port; you plug another doohickey in another outlet elsewhere in your house, with another Ethernet cable, either directly into a device like your DVD player, or into a multi-port switch to support multiple wired devices.

You can find these so-called "HomePlug" kits from major networking vendors like Netgear, Linksys, and Belkin. That said, user reports vary in how fast real-world speeds are with powerline networks. One major variable will be the quality of wiring (and insulation from interference) in your home. Also, expect to spend close to $100 to enjoy HomePlug convenience.

If you'd like to spend even more money, consider the Ubiquiti Airwire. Essentially behaving like a wireless bridge, you plug one doohickey into your router and another doohickey into a wired LAN port such as your DVD player or, again, a multi-port switch. The difference from HomePlug is that these two doohickeys communicate wirelessly rather than by your powerlines. Performance is theoretically several times faster than HomePlug, but like any wireless link, quality will depend on distance and other environmental factors.

Finally, if you would like to spend very little money and earn some hacker cred in the process, create your own wireless bridge. You can do this quite easily using one of the popular open-source firmwares such as DD-WRT or Tomato. See the linked tutorials for both instructions and how to find compatible routers. Once you know what you're looking for, you can probably pick up a supported router on eBay secondhand for $20. Voila, cheap wireless bridge, and your Blu-Ray player will be online with no messy cabling.



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