Public Wi-Fi: Know the Risks and Stay Protected

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Post Published On: February 13, 2019

“Free Wi-Fi” – the notice declares. Weary shoppers throng into the coffee shop, drawn by the prospects of Internet access at no cost whilst, perhaps, enjoying a warm cuppa with some cake. Public Wi-Fi is a basic necessity at hotel lobbies, malls and coffee-shops, rather than a fancy accessory. Not only do they attract foot-fall, they also retain it and thereby, promote sales. The cable-free convenience that Wi-Fi affords us has heightened its popularity and today, at least within developed economies, Wi-Fi is everywhere. However, that is not the problem.

We connect to open, public Wi-Fi hotspots almost intuitively. The process of swiping across our screens, scanning through available wireless networks and connecting to the most appropriately labeled one (“Free<MallName>Wi-Fi” anyone?) is so natural, seamless even, that we rarely spare it a second thought. Take the average tech-user, someone who knows how to use technology, but not how it works, and put them in this spot. You have the ideal target of a cyber-criminal. Today, just about anyone with a smartphone is a potential user – and a potential victim. Unless, of course, they are aware of the Cyber Security risks and take appropriate measures to protect themselves.

There are two primary drivers of cybercriminal intent over a public Wi-Fi network. Let us look at them

Intent 1: Data Theft:

The intent of the cyber-criminal is to steal sensitive data such as credit card numbers, banking passwords, end-users’ work-related files, etc.

a)      The Evil Twin

In an evil twin attack, a fake wireless hotspot is set up, impersonating a genuine Wi-Fi network. It lures end-users to connect by advertising a stronger network signal, and of course with an SSID that sounds relevant (“Free<MallName>Wi-Fi” again).

Once connected, the evil twin typically routes all user traffic over to the genuine hotspot, so that victims will continue to access the Internet and no eyebrows are raised. However, unbeknownst to the victims, the evil twin hotspot is firing on all cylinders in the background, intercepting their web-traffic and scouring it for sensitive data. Any passwords or credit card numbers typed into a web-page over an unencrypted connection (for instance, HTTP instead of HTTPS) is compromised.

b)     Cracking Wi-Fi Encryption

An open Wi-Fi network, one to which anyone can connect with no password whatsoever, does not encrypt traffic. Strictly use these only for public activities like Googling or Wikipedia.

Wi-Fi networks that require a password encrypt all traffic. However, how quickly a cybercriminal can crack the encryption depends on the protocols used. Most Wi-Fi routers implement WEP, WPA or WPA-2 encryption. Cracking WEP is a trivial affair. If you see a public Wi-Fi hotspot on WEP, stay away.

WPA-2 encryption is based on a key that is pre-shared between the end-user and the Wi-Fi host. Remember asking the cashier if you could have the Wi-Fi password? WPA-2 offers the best protection on the list but has also been recently cracked. Despite this, most public Wi-Fi networks do not implement anything stronger – like WPA-2 in 802.11i mode for instance.

A hacker sitting in the vicinity of the hotspot, can use tools like WireShark, AirCrack-ng, kismet, etc.  to monitor all Wi-Fi traffic and potentially decrypt your passwords, or confidential documents.

Intent 2: Circulate Malware:

The second, and no less nefarious intent is to disseminate malware on the devices of unsuspecting users connected to a Wi-Fi network.

a)      Coffee Miner

If you’ve noticed that your phone has been acting unusually slow ever since you returned from that business trip, consider the possibility that it has mining malware running on it, contracted when you connected to the open airport Wi-Fi.

Close on the heels of the cryptocurrency wave, 2018 saw the rise of a new form of cyber-crime called Cryptojacking. Given the resource-hungry nature of cryptocurrency mining, cyber-criminals connived methods to illegally harness CPU power from other computers and fuel their own quests for Bitcoin-glory.

In the Coffee Miner attack, the attacker first intercepts traffic between your device and the public Wi-Fi router. Once they have visibility over the web-pages you are spending most time on, a JavaScript code is injected into those web-pages. When you visit the page again, or reload it, the mining malware is installed on your device. Coffee Miner attacks are notorious for overloading victims’ phones to the extent that their batteries begin to over-heat and swell, effectively bricking the device.

b)     File Sharing

Another scenario exploits the use of Wi-Fi to deliver high speed file transfers between end-users on the same hotspot. Although security sense dictates that such transfers must be carried out only within closed and trusted wireless networks, it is not always the case. Hackers have successfully exploited ill-founded trust relationships on public Wi-Fi networks to infect victims’ devices with viruses and ransomware.

Staying Protected:

  1. Educate yourself on the risks of wireless networks. Awareness is the fundamental defense tactic.
  2. Disable file sharing both on your laptop and your mobile. If that’s not an option, ensure you accept incoming file transfers only from verified and trusted senders.
  3. Turn off Wi-Fi when you’re not using your device. Besides improving battery life, this prevents your device from latching on to remembered wireless networks without your knowledge, and exposing you, potentially, to an Evil Twin.
  4. Avoid open Wi-Fi. When anyone can connect with no authentication required, Open Wi-Fi is a sort of Utopian playground for hackers on the lookout for your data. In contrast, the far more restrictive closed ecosystem of a WPA-2 encrypted network begets better trust.
  5. Configure your browser to only accept HTTPS connections and to reject HTTP traffic by default.
  6. Within the permits of local laws and regulation, use a VPN. Regardless of the type of encryption the public hotspot implements, the VPN tunnel adds a layer of encryption over all your data, making it harder for an interceptor to use it.
  7. Save sensitive transactions for later. Avoid accessing sensitive websites including your internet banking portal, social media, work mail, etc. when connected over an open public network. If this is not avoidable, ensure you have enforced two-factor authentication on these accounts, so even if your password is compromised, your account may still not be taken over.
  8. Use an updated anti-virus tool on your device and configure it to run scans at scheduled intervals. Also ensure all applications on your device are patched and updated. This greatly improves your chances at fending off cyber-attacks and malware.

Article Written by Praveen Joseph Vackayil – Cyber Security Consultant and Trainer

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