Public Wi-Fi networks have become part of everyday life, offering free connectivity in places such as cafés, hotels, airports and public spaces. However, this convenience comes with serious security risks. Because these networks are so easy to access, they are also frequent targets for cybercriminals seeking to steal personal and business information.
In this article, we look at the main types of attacks on public Wi-Fi networks, the risks involved and, most importantly, the best practices for protecting data when using these networks. For companies and users of document management platforms, understanding the dangers of open Wi-Fi networks and implementing security measures can be essential to prevent leaks of confidential information.
Main types of attacks on public Wi-Fi networks
Cybercriminals use several techniques to compromise the security of these networks. Below, we describe the most common methods:
Man-in-the-Middle (MitM) attacks
Man-in-the-Middle attacks are among the most common threats on these networks. This type of attack occurs when a hacker manages to intercept the communication between the user and the access point, positioning themselves “in the middle” of the connection. In this way, the cybercriminal can read, modify or even redirect traffic without the user noticing.
These attacks are particularly dangerous on networks with no encryption or weak encryption, where communication is not properly protected. As a result, attackers can easily capture confidential information, such as login credentials, banking details and private messages.
Fake Wi-Fi networks (Evil Twin)
Another widely used type of attack is the creation of fake Wi-Fi networks, also known as “Evil Twin”. In this scenario, the attacker creates a Wi-Fi network that mimics the name (SSID) of a legitimate network. When users inadvertently connect to this fake network, the attacker can intercept and store their data.
Moreover, attackers often set up these fake networks in busy public places, where users may not question the authenticity of a free Wi-Fi network.
Packet sniffing
Packet sniffing is a technique used to capture and analyse the traffic flowing across a network. On public networks, where traffic is not always encrypted, cybercriminals can use sniffing tools to capture the communications of other users on the same network. Consequently, they can access sensitive information, such as passwords, credit card numbers and work communications.
DNS spoofing attacks
DNS spoofing attacks involve manipulating the DNS servers that translate domain names (such as www.exemplo.com) into IP addresses. By compromising these servers, cybercriminals can redirect users to fake websites, where they are led to enter personal data in the belief that they are on a legitimate site. This type of attack is especially dangerous on open networks, where defences are generally weaker.
Security risks on public Wi-Fi networks
Attacks on public Wi-Fi networks can have serious consequences for both individual users and businesses. The main risks include:
Identity theft
Capturing login credentials, such as usernames and passwords, allows cybercriminals to access personal and business accounts. With this information, they can commit fraud and identity theft and compromise confidential information.
Access to sensitive data on public Wi-Fi networks
When using these networks, users risk exposing confidential data, such as emails, business documents and financial information. For this reason, companies that allow employees to access sensitive data over these networks are particularly vulnerable.
Malware installation via public Wi-Fi networks
In some cases, cybercriminals use these networks as a way to distribute malware. To do so, they rely on unauthorised downloads or redirect users to malicious websites. The malware installed can then compromise the user’s entire system and, in more serious cases, allow remote control of the device.
Best practices for using public Wi-Fi networks safely
Despite the risks, you can minimise exposure to attacks when using these networks by following a few recommended security practices:
Use a VPN (Virtual Private Network)
A VPN creates an encrypted tunnel between the user’s device and the VPN server. In doing so, it ensures that all communications are protected, even on unsecured networks. Therefore, with an active VPN, cybercriminals cannot read the data transmitted, which makes communication significantly more secure.
Turn off automatic connection to Wi-Fi networks
Many devices are set up to connect automatically to open Wi-Fi networks without asking for the user’s permission. Turning off this feature can therefore prevent the device from connecting to fake networks without your knowledge.
Avoid sensitive activities on public Wi-Fi networks
When using a public Wi-Fi network, it is advisable to avoid sensitive activities, such as accessing bank accounts, exchanging confidential information or downloading business documents. However, if you need to carry them out, it is better to use a VPN or a secure mobile network.
Check SSL certificates
Whenever you visit websites that require login credentials or handle confidential information, it is important to check that the site uses HTTPS and has a valid SSL certificate. Indeed, HTTPS websites encrypt communications between the browser and the server.
Keep software up to date
Cybercriminals often exploit vulnerabilities in outdated software to compromise devices. For this reason, always keeping the operating system, browsers and security software up to date is essential to minimise the risk of attacks.
Turn off file sharing
When using a public Wi-Fi network, turning off file sharing on your device can prevent other users on the network from inadvertently accessing documents and folders. To do this, simply adjust the operating system’s network settings.
Mobility policy for employees
For companies, protection cannot rely solely on each employee’s common sense. It is therefore advisable to define a simple policy for working off site, with clear rules on public networks.
- always use the company VPN when not on a trusted network;
- use your phone’s mobile hotspot rather than open Wi-Fi networks;
- enable multi-factor authentication on all business platforms;
- keep disk encryption enabled on laptops;
- report any unusual device behaviour immediately.
In addition, the IT team can configure devices so that the VPN connects automatically. As a result, protection no longer depends on a decision by the user each time.
Practical example: A technician on the road
Imagine a safety technician at a motorway service station who needs to upload a site visit report to the document management platform. The free Wi-Fi network appears with the service station’s name, but there are two networks with almost identical names.
Instead of choosing one of them, the technician uses their phone’s mobile hotspot and connects to the company VPN. They then access the platform via their usual bookmark and check for the padlock in the browser. In this way, they avoid a possible fake network and protect the credentials and documents they transmit.
Signs that a network may be fake
A few clues help identify suspicious networks before you connect. For example, you should be wary of two networks with almost identical names in the same place, an open network named after a hotel that normally asks for a password, or a login page that requests excessive personal data. Furthermore, invalid certificate warnings in the browser right after connecting are a clear warning sign. In such cases, the safest option is to disconnect immediately and use mobile data. Finally, it is worth confirming the correct network name with staff on site.
Frequently asked questions
Is HTTPS enough to stay safe on a public network?
HTTPS protects the content of your communication with the site, but it does not prevent every risk, such as fake networks, phishing pages or malware. It should therefore be combined with a VPN, multi-factor authentication and attention to browser warnings.
Are password-protected Wi-Fi networks safe?
They are safer than open networks, especially with WPA3. However, when the password is shared by all customers, other users on the same network still pose a risk.
Is it safe to access the document management platform from a hotel?
It can be, provided you use the company VPN, multi-factor authentication and an up-to-date device. Even so, whenever possible, use mobile data for tasks involving sensitive documents.
Conclusion
Public Wi-Fi networks offer undeniable convenience, but they also present a range of risks that can compromise the security of personal and business data. For users of document management platforms and companies that handle sensitive information, it is essential to be aware of these threats and adopt appropriate security practices.
Measures such as using a VPN, avoiding sensitive activities and checking SSL certificates can significantly reduce the risk of attacks. For further recommendations, see the Portuguese National Cybersecurity Centre (CNCS). Ultimately, digital security is a responsibility shared between users and organisations, and data protection should always be a priority.
Read also: Who hackers are, how they operate and how to protect yourself and Protection against Man-in-the-Middle attacks.