Dangers of using “Public Wi-Fi”

The pervasiveness of free Public Wi-Fi at hotels, airports, coffee shops makes staying connected while out of the office very simple and convenient.  However, it is not without risk.  There are several mechanisms by which attackers can take advantage of the openness of these networks for their own gain.  I have been researching this topic and would like to identify the most common types of risks and ways you can protect yourself from being exposed to these risks.

What are the risks?

The fact that you do not have any knowledge of who or what is connected to the free Wi-Fi networks at the same time as you poses several risks.  Some of the techniques used to exploit public Wi-Fi networks are listed below.

  • The Wi-Fi hotspot may be a rogue “Ad Hoc” network running off of a PC or Laptop instead of an actual Wi-Fi access point.
  • “Wireless Isolation” may not be enabled so other devices connected to the Wi-Fi have connectivity to your device.
  • The Wi-Fi hotspot may be masquerading as an access point with the same SSID as what your laptop, phone or tablet has connected to in the past.

Rogue Ad-Hoc networks

A common implementation of this is a device broadcasting an SSID of “Free Public Wi-Fi”.  These are almost always fake and designed to lure people into connecting so the attacker can intercept the data transmitted from the victim’s PC.

Wireless Isolation Disabled

Even if the Wi-Fi access point is legitimate, security measures to protect you from others on the Wi-Fi network may not be enabled.  Most wireless access points have the ability to segment users from each other by not allowing Wi-Fi clients to communicate with each other.  This is called “Wireless Isolation”.  If this is disabled there is nothing stopping a criminal from attempting to exploit vulnerabilities on your device.  Many public Wi-Fi hotspots do not disclose whether Wireless-Isolation is enabled.

Masquerading Wi-Fi Access Point

Your devices remember the wireless networks that you have connected to.  This is convenient because it allows you to seamlessly connect to Wi-Fi networks you use often without any manual configuration.  The drawback is that devices exist that will see your devices searching for these networks and masquerade themselves as a wireless network you have connected to before.  Your device will connect to them and data transmitted from your device can be intercepted.

What You Can Do To Protect Yourself

  1. Don’t ever connect a network with an SSID like “Free Public Wi-Fi”.
  2. Use HTTPS equivalents when logging onto sites that require logon information or contain sensitive information.  Additionally, you shouldn’t proceed to sites that present you with certificate errors while connected to a public Wi-Fi.
  3. Find out if staff at the facility offering free Wi-Fi knows if Wireless Isolation is enabled.
  4. Make sure your Windows Firewall (or Antivirus Firewall) is turned on while using your laptop on a Public wireless network.
  5. Utilize VPN software to connect securely.  This isn’t the type of VPN technology that you use to connect into your work network while offsite.  It is software that you can put on your laptop, phone or tablet that securely connects to the Internet via an encrypted tunnel.  All of your Internet traffic (email, web browsing, etc) is securely transmitted through this encrypted tunnel.  Even if you were on an insecure Wi-Fi network an attacker would not be able to decipher the traffic that was being intercepted from your machine.   An example of a service like this is Witopia VPN (http://www.witopia.com).


Public Wi-Fi has become a necessity for many of us when traveling for business or pleasure.  However, failing to educate and protect ourselves from attacks on our mobile devices can result in our privacy and sensitive accounts being compromised.  Following some general “best practice” guidelines when using public wireless networks can protect you from most of these attacks.  However, the best security is achieved by encrypting traffic while on these public networks by utilizing VPN software.

by Shane Linde, Senior Engineer








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