Airports, coffee shops, restaurants, technically-challenged neighbors — free WiFi is everywhere, and it’s great. You can save data on your phone and take your work on the road without worrying about finding a connection. But these networks aren’t always safe. Some of them are specifically set up to harvest your data, and even networks you trust can be vulnerable. Indeed, if you’ve used public WiFi with any frequency, you’ve probably had someone snoop on you using one of these methods.
Packet-sniffers are programs that hunt for and record any unencrypted data being sent or received on a WiFi network. If you are using open WiFi, which has no encryption by default, you should assume that everything you do may be showing up on someone else’s computer. The network itself may be innocent – just your local coffee shop, for example – but all a hacker on the same connection needs to do to spy on you is run a free program.
Your site visits, keystrokes, and even site cookies and login data can be vacuumed up without you knowing it, the exception being any website that uses SSL/TLS end-to-end encryption. If you see https:// at the beginning of the site address, packet sniffers usually cannot see what you are doing. Don’t get too comfortable, though; there are tools to break HTTPS encryption.
You should also assume that you are vulnerable on a WEP-encrypted network, as its encryption is very easy to crack. If you are on a WPA or WPA2 network, you are much more secure, as all of your data is automatically encrypted. However, dedicated attackers who are already connected to the same network can watch your computer connect and find out your unique encryption key which they can use to see, again, everything you are sending and receiving. Even if you are already connected the attacker could send your computer a fake command to log off and then grab your key when you log on again.
WiFi Spoofing, Evil Twins, and Man-in-the-Middle
“Spoofing” a WiFi network simply means copying it, which can create an “Evil Twin” – a network that looks and behaves identically, or at least similarly, to a legitimate network. If the attacker sets up a router with the same name and password as one of your habitual networks, you probably won’t give it a second thought when you connect or your computer connects automatically. The attacker can even log on to the legitimate network, send a disconnect command to the computers on it, and then snag the devices that automatically reconnect to the evil twin.
Once the attacker has an evil twin network with users on it, he becomes a “Man in the Middle,” which is just what it sounds like: a central access point that logs all the data you send or receive through it. That doesn’t sound a lot worse than packet-sniffing, but it can be. Since the attacker controls your access to the Internet, what you ask for won’t necessarily be what you receive. If you try to log on to your bank, the attacker may reroute you to a website with a similar name and similar design in the hopes that you’ll enter your login information there.
Man-in-the-Middle attacks don’t necessarily have to involve an Evil Twin, though. Especially in high-traffic public areas where bogus Wi-Fi will go unnoticed, someone might just create a random open network offering “Free Airport WiFi” and wait for people to connect to it. If a network asks you for your credit card to pay for airtime, you should definitely double-check its credentials.
How do I stay safe?
Does this mean you should never connect to an open WiFi network ever again? No, open networks are fine if you take a few precautions.
1. Get a VPN (Virtual Private Network), which will take your sent and received data, encrypt it, and channel it through a server somewhere else. While they don’t guarantee 100% protection, especially against a determined attacker, they will usually stop you from being selected as an easy target.
2. Install a browser add-on like Https Everywhere which forces all websites to use end-to-end encryption if available. Packet-sniffing software usually can’t see through encryption, though it can still see where you’re going.
3. It’s very hard to tell an evil twin apart from a legitimate network, but you can still remain vigilant for any funny business. If “https://mybank.com/login” suddenly becomes “http://mydank.com/login,” you’ll want to get off that network.
You will never be 100% safe or private online, even on your home network. If someone wants to hack you, they probably can. The best anyone can really do is take reasonable precautions. If you always use common sense, a VPN, and HTTPS on public WiFi, you can minimize the risks posed by fraudulent networks.