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Tuesday, January 17, 2006

Is your laptop faithful? New simple wireless flaw

During the weekend, well-known security researcher Simple nomad released some information about a vulnerability that could be exploited to gain access to an unsuspecting laptop using a wireless connection. How does the exploit work? I tested it myself with 2 laptops that were available in the company I work for, and it works beautifully.

You probably all know that a wireless laptop can be configured to advertise an ad-hoc connection to the surrounding world right? When a computer is configured this way, it's asking to other computers in the vicinity to connect to it.

Let’s say that I have a laptop that is configured to connect to my wireless network at home. In this case, the configured SSID is the default one that linksys APs uses in general: "Linksys", so my wireless NIC is also configured to use it. If I walk in a location where there is a second laptop broadcasting an ad-hoc network, which, by chance, is also using the "linksys" SSID, my own laptop will connect to it. Everything is working like it should up to this point right? This is where the problem starts. The next time my computer boots in a location where there is no wireless network with a "Linksys" ID , it will start advertising its own ad-hoc network with that SSID, even if it was first configured to be in infrastructure mode. At this point, an attacker could get access to your system if:

  • You firewall is off
  • Your firewall is ON, but you're missing a few critical windows patches that could let a villain exploit some vulnerability.

Solution / Workaround : Simple Nomad wrote about 3 possible workaround to help you stay protected:

  • Disable wireless when not in use.
  • Do not use the Windows wireless client manager, but an alternate one (e.g. for an integrated Intel Wifi
    connector, use Intel PROSet/Wireless) as all others tested do not seem to have the problem (this testing was not all-inclusive).
  • Click on the Wireless option in the System Tray and open the Wireless Network Connection window. - Click on "Change advanced settings". - In the Wireless Network Connection Properties window, click on the Wireless Networks tab. - Click on the advanced button. - Click on "Access point (infrastructure) networks only" . This is the recommended workaround.

This workaround prevents you from connecting to any ad-hoc network in the first place. Please don't forget to enable your windows firewall and keep those patches up to date. This won't prevent people from connecting to you, but it will stop them from getting access to your computer.


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