Is public Wi-Fi less secure?

Public Wi-Fi networks can insert ads or require information to connect, but the risk of users having their data stolen is not high.

When accessing free Wi-Fi at a supermarket or coffee shop, users will see a screen with advertisements provided by the business, asking to enter information and accept terms to access the Internet.

Usually, these websites are not dangerous. However, some Wi-Fi networks can insert ads while browsing the web, even fraudulent ads that put users at risk.

A public Wi-Fi access tower in New York (USA). (Photo: Bloomberg).

Reasons why public Wi-Fi uses a login website

Wi-Fi networks are often secured in a variety of ways. Typically, personal or small business networks use the PSK (Pre-Shared Key) mechanism, which requires entering a pre-shared passphrase to connect.

Meanwhile, public Wi-Fi networks at cafes, shopping centers, airports. use a password-less login method called captive portal.

With this mechanism, users can connect to the network and get an IP address from the router, but cannot access the Internet. Instead, they are directed to a login website with a business image, login information and can advertise.

To test Internet connection on public Wi-Fi, the device will send requests to test addresses, for example captive.apple.com on iPhone. If you receive the result 'Success!' (success), meaning the user can access the Internet.

On the contrary, if the router blocks access or needs to authenticate via captive portal, the device will automatically open the browser and go to the login page provided by the router.

A Starbucks Wi-Fi connection page (captive portal). (Photo: Nil).

Depending on the network, users will enter different information. Some networks require employee email login, cafes provide passwords, public locations only need to ask for name/age, accept terms. to authenticate and access the Internet.

Different from conventional security mechanisms, captive portal allows businesses to manage connections more flexibly. According to Tech Target, coffee shops can calculate the time to block access when the time is up, while businesses use the information to analyze customers and display ads.

Many Wi-Fi routers today support guest mode with captive portal. Open source software such as NoCatSplash, ChilliSpot allows creating captive portals, redirecting users to them to connect to Wi-Fi.

Overall, captive portal makes advertising when using corporate Wi-Fi simpler.

Besides ads in the captive portal, connection owners can direct users to websites containing ads while surfing the web, or when clicking certain links.

However, compared to captive portal, this method requires more techniques, such as adjusting DNS and proxy from the router side to interfere with the connection every time the user clicks on the link.

Not many popular devices support this feature, and websites using the HTTPS protocol will not work. Inserting ads into Wi-Fi networks can also be annoying, or worse, deceptive advertising.

Is public Wi-Fi safe?

Although very useful , public Wi-Fi at airports or coffee shops is always considered unsafe.

However, security experts say that with common tasks such as watching movies, accessing social networks. hackers will have nothing to take over.

'That type of data is not only less valuable but also high risk. If I can get your password from Moldova and not be in danger, why should I get on a plane and go to your local Starbucks?', Chester Wisniewski, Global CTO at security firm Sophos , said.

Wi-Fi settings screen on iPhone. (Photo: 9to5Mac).

Previously, the majority of web traffic was not encrypted. Anyone can see what websites other people visit, if they successfully penetrate their network.

By 2017, Firefox said more than 50% of web traffic used the HTTPS encryption protocol. That means that even when using public networks to steal data, hackers cannot get valuable information.

Russ Housley, founder of cybersecurity company Vigil Security, said if users regularly work with sensitive data, users can download a virtual private network (VPN) tool.

These apps support hiding IP addresses to hide activities, even block ads and reduce the risk of cyber attacks.

Instead of worrying about public Wi-Fi being less secure, the Washington Post advises users to set strong passwords, regularly update software and grasp scams to proactively prevent them.

'In general, using public Wi-Fi is safe as long as your computer is updated to the new version, and the data is encrypted,' emphasized Eric Rescorla, former Chief Technology Officer at Mozilla.