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How dangerous is public Wi-Fi? We ask an expert

How often have you been stuck in an airport, or on a train, and decided to take advantage of the public Wi-Fi network? Do you choose restaurants or cafes based on their free Wi-Fi? Great. Now, answer this: What do you do on your smartphone or laptop when you connect? I know it’s none of my business, but if you aren’t protecting yourself, snoopers and cyber criminals may have a field day at your expense.

Public Wi-Fi is everywhere. We all use it, but most of us are unaware of the risks and fail to take the necessary precautions to protect ourselves.

“The major hazard with public Wi-Fi is the fact that all the information you’re transferring between your computer and the computer that you’re accessing is available to everybody on the network,” explains David Maimon, Assistant Professor in the department of Criminology and Criminal Justice at the University of Maryland. “What attackers do is try to intercept the communication between your computer and the computer you’re trying to get information from or send information to. They can get passwords, usernames, you name it.”

Maimon is in the midst of a study into how we use public Wi-Fi networks. He has been visiting locations across Maryland, connecting to public Wi-Fi networks, and collecting data.

The 3 dangerous amigos of public Wi-Fi

There are three common avenues of attack to worry about with public Wi-Fi: man-in-the-middle attacks, malware, and Wi-Fi sniffing.

Main-in-the-middle attacks: “Man-in-the-middle attacks are where attackers are putting together their own network and standing between your computer and the computer you’re trying to access and all the information is routed through their device,” Maimon explains. “If they use this kind of approach then all the information is accessible to them, it doesn’t matter if you are accessing an HTTPS website, an encrypted website or not.”

“I can pretty much see whatever you’re doing on your computer…”

Malware: Malware is even more dangerous, because it potentially gives an attacker access to everything on your device. They can steal your files or photos, and even turn on cameras or microphones to eavesdrop. If the attacker can get your login info for a cloud service, for example, it’s easy for them to slip malware onto your device.

Wi-Fi sniffing: The last method is known as Wi-Fi sniffing and it involves monitoring network traffic. Attackers record huge swathes of data as it travels across the network and then analyze it later to uncover useful details. Sadly, it’s not even illegal to sniff through packets a lot of the time.

“When we started we had to get approval and the legal team in Maryland checked whether it’s okay to sniff and couldn’t find any law preventing you from sniffing,” says Maimon. “Banners before you log in to public Wi-Fi, where you agree terms of use, sometimes specifically mention you’re not allowed to sniff and that makes it illegal, but if there’s no banner then it’s not illegal at all.”

It’s alarmingly easy to snoop

You might imagine that you’d need expensive specialist equipment or some kind of programming ability to monitor Wi-Fi and get your hands on other people’s information, but you don’t. Maimon uses the same tools that the hackers use and they are very easy to get your hands on.

“You can turn on Wi-Fi sniffing, log into a public Wi-Fi network and the software allows you to listen to and see all the traffic that’s transferred over the network,” Maimon explains. “I can pretty much see whatever you’re doing on your computer.”

Pineapple Wi-Fi device

For man-in-the-middle attacks, you can buy devices online and operate them without being a computer science student.

“One of the tools that the hackers are using is the Pineapple Wi-Fi device — it helps them generate spoofed websites,” says Maimon. “All the information is routed through the device. You think you’re sending it to the HTTPS website, but it’s actually a spoof website that the device created.”

Related: Should you worry about malware on your phone?

Unless you’re snooping yourself, there’s no way to tell if you’re being exposed on a public Wi-Fi network. There’s no easy way to detect sniffing or man-in-the-middle attacks.

How do you protect yourself?

“When you’re on a public Wi-Fi network don’t access your bank account and sensitive details,” says Maimon. “Even Facebook and email, sometimes you send sensitive information over emails, if you don’t want to expose information, don’t use these things on public Wi-Fi. Use it for Web browsing or using Netflix maybe, but nothing else.”

Remember, the apps on your phone may automatically transmit data in the background, as well. Follow our advice on how to limit your background data on iPhone or Android.

“If you don’t know who’s running the network then you probably shouldn’t use it.”

You also have to make sure that you’re connecting to the right network. The next stage in Maimon’s research is to travel around public areas with his own unsecured Wi-Fi hotspot and see how many people connect and what they do. He has been surprised by how readily people will connect to networks that they know nothing about.

“If you don’t know who’s running the network then you probably shouldn’t use it,” he says. “You’re taking the risk that it’s a bad guy operating it.”

You should also stop your devices from automatically connecting to public Wi-Fi whenever it’s available, just in case it connects to a dodgy network. Criminals will set up their own hotspots in busy areas, so always ask the café owner or someone who works at the location for the connection details to make sure you’re connecting to a legitimate network.

If you’re willing to expend a little effort, there’s also another way to keep yourself safe.

“A VPN service is the best way to go. All the information you transfer is protected, it’s like a tunnel that protects the data from attackers,” says Maimon.

Protect yourself with a VPN service

“I think people should use public Wi-Fi because it’s becoming more ubiquitous as the Internet spreads, when people are traveling and they’re outside their house they should use it,” says Golden Frog president, Sunday Yokubaitis. “But they need to protect themselves and be aware of the dangers.”

VPN stands for virtual private network, and there are many services out there that you can use with apps for smartphones and computers. Golden Frog is the company behind one of the most popular VPN services around: VyprVPN.

“Users connect to our servers using an encrypted connection, really protecting that last mile,” explains Yokubaitis. “It wraps the entire internet connection in encryption and keeps you protected, protecting beyond the Wi-Fi router all the way to our servers.”

If you’re using a VPN then snoopers engaging in Wi-Fi sniffing won’t be able to see what you’re up to. Stronger protocols like OpenVPN can also defeat man-in-the-middle attacks. But this protection comes at a price, and you should choose your service carefully.

Related: Is your smartphone being tracked?

“You may be protected from public Wi-Fi, but end up with a provider with a business model predicated upon selling your data,” explains Yokubaitis. “The price of free is too high. A VPN service requires network, and servers. If it’s free, you really need to look into the business model.”

There have been a few scandals in the VPN space. Hola was found to be selling user’s bandwidth, though it’s not actually a VPN; it’s a proxy service. A Chinese provider called Terracotta was also recently exposed by RSA Research for selling stolen infrastructure access to hackers.

A VPN service is the best protection you can employ if you’re going to use public Wi-Fi.

If you’re concerned about privacy then you may raise an eyebrow at VPN services owned by the likes of Facebook and App Annie. Data analysis and sales is big money. You could be giving up more than you realize.

“This isn’t just demographic data like another website might sell, this is every website you’re visiting, every app on your phone,” says Yokubaitis. “Think of it like dropping your kids off at daycare, you’re relinquishing control, and in order to do that you really need to look into who you’re dealing with.”

A VPN service is the best protection you can employ if you’re going to use public Wi-Fi, just make sure that you choose carefully. Read the privacy policy, check the provider’s background and location, and do a little research.

If you plan on using public Wi-Fi without one, make sure that you’re connecting to the right network and don’t access anything sensitive, like your bank account. It’s simply not worth the risk.