- Disabling automatic connection and forgetting public WiFi networks drastically reduces the risk of data exposure.
- Vulnerabilities in WPA2 and the use of open networks facilitate interception, malware, and spoofing attacks.
- Properly configuring the router (WPA2/WPA3, strong passwords, MAC filtering) limits intruder access to the home network.
- Complementing these measures with VPNs, updates, and good password practices strengthens overall security.
Connecting to the first free Wi-Fi network that appears on your phone has become almost automatic , especially when you're out and about and don't want to use up your data. The problem is that behind many of these open or poorly secured networks, cybercriminals may be waiting to intercept sensitive information such as passwords, bank details, or personal emails. And to make matters worse, many devices connect automatically without even asking for permission.
Avoiding automatic connections to unsecured Wi-Fi networks isn't complicated, but it does require changing some habits and carefully reviewing the settings of both your mobile phone and your home router. Disabling automatic connections, "forgetting" networks you no longer use, taking advantage of security features like WPA2/WPA3, or even filtering by MAC address are key steps to reducing risks and keeping your data safe every day.
Why public and insecure WiFi networks are dangerous
Wireless networks in airports, train stations, hotels, restaurants, and other public spaces are a magnet for users , but also for attackers. On vacation, business trips, or simply when going for a coffee, it's very common to connect to the Wi-Fi without considering its security level or who is behind the network.
When using a public or unsecured WiFi network, we can suffer different types of cyberattacks : from simple traffic interception to more complex techniques where communications are modified, web pages are redirected to fake sites, or phishing and vishing campaigns (fraudulent calls) are launched taking advantage of the captured information.
One of the most dangerous scenarios involves fraudulent networks that mimic legitimate networks , also known as "evil twins" or decoy networks. An attacker creates an access point with a name similar to that of the hotel, station, or restaurant, and many users connect without realizing that all their traffic passes through the cybercriminal's device.
In this context, leaving the automatic Wi-Fi connection option enabled increases the risk , as the phone can connect to an open or poorly configured network without warning while walking down the street or through a shopping mall. Often, the user isn't even aware that they've switched networks and are sending data through a completely unsecured environment.
Security flaws in WPA2 and the exposure of WiFi traffic
Although WPA2 has been considered the most secure protocol for home and corporate Wi-Fi networks for years , critical vulnerabilities have been discovered that affect both access points (routers, APs) and clients (mobile phones, computers, tablets, IoT devices, etc.). One of the best-known is the KRACK (Key Installation Attacks) suite.
KRACK attacks exploit the key exchange process between the router and the device during the WPA2 handshake. By manipulating this exchange, an attacker within range of the network can force the reuse of encryption keys and ultimately decrypt traffic that, in theory, should be end-to-end protected.
The impact of this vulnerability is very serious because the content of communications can be exposed : login credentials, credit card numbers, banking information, emails, private messages, personal data, and virtually anything transmitted without an additional layer of encryption (such as a well-implemented HTTPS or a VPN). Furthermore, depending on the network configuration, malicious traffic can also be injected.
Most manufacturers (Apple, Google/Android, Microsoft, Linux, etc.) have released patches to mitigate these vulnerabilities , but many older or outdated devices remain vulnerable. Therefore, it's crucial to keep your router's operating system and firmware up to date and enable automatic updates whenever possible.
Risks of leaving WiFi always on on your mobile phone
In Spain, many users leave their mobile Wi-Fi permanently switched on, both at home and on the street . It's convenient because the phone automatically switches between networks, but from a cybersecurity perspective, it's a highly inadvisable practice, as the National Cybersecurity Institute (INCIBE) warns.
When Wi-Fi is always on, the device spends all day searching for networks to connect to , and if automatic connection is enabled, it will automatically connect to any open or previously known networks that appear. In an environment with many fake or manipulated networks, this opens the door for an attacker to intercept or manipulate our data.
INCIBE emphasizes that cybercriminals exploit these lapses to intercept communications and steal sensitive information. On open, unencrypted networks, anyone with basic knowledge can spy on the traffic of other users on the same network, especially if they access websites without HTTPS or use misconfigured applications.
Added to this is the risk of malware, which often goes largely unnoticed by the average user . Insecure connections and outdated devices are the perfect combination for Trojans, spyware, ransomware, or other types of malicious software to infiltrate systems, steal data, spy on communications, or even give the attacker remote control of the device.
How to disable automatic connections on your mobile phone
The first step to prevent your phone from automatically connecting to unsecured Wi-Fi networks is to check your automatic connection settings . Both Android and iOS allow you to choose which networks your device connects to and which it doesn't, although this option is sometimes hidden and the interface can be confusing.
Typically, the system automatically connects to networks we've already connected to , saving the password so we don't have to enter it each time. On many phones, you can also enable or disable automatic connection individually for each network, allowing you to keep it enabled at home or work and disable it in bars, hotels, or other locations where you don't fully trust the security.
On Android, you'll typically go to Settings > Network & Internet (or Connections) > Wi-Fi , tap the name of the specific network, and look for a box like "Connect automatically" or something similar. Unchecking this option will prevent your phone from automatically connecting to that network, although it will still appear in the list so you can connect manually whenever you want.
On iOS, the process usually involves going to Settings > Wi-Fi, tapping the network information icon (the "i") , and disabling the automatic connection option if available. You can also tell your iPhone to "forget" that network by deleting the password and any associated settings, forcing a new connection request when you encounter it again in the future.
Forget WiFi networks and clear the list of saved connections
Every time we connect to a Wi-Fi network, the device tends to save it for future use . This is great for our regular networks (home, work, relatives' houses), but not so much for public networks in hotels, cafes, shops, or public transport that we use once and never need again.
If we don't remove these networks, our phone can automatically reconnect when we pass nearby again , even years later, with the same security risks as always. Therefore, a good practice is to occasionally review the list of saved networks and "forget" any that we don't want to use again.
The process is usually very similar on most devices : go to Wi-Fi settings, find the saved or known networks section, tap on the network you want to delete, and select the "Forget," "Delete," or similar option. When you do this, your phone will disconnect, and although the network will still appear as available, it will no longer automatically connect.
If we decide to use that network again at any point, we'll simply have to enter the password again . It might seem like a minor inconvenience, but it's one of the most effective ways to maintain control over which networks our device actually connects to and avoid surprises when we're in untrusted locations.
By regularly cleaning this list, we also reduce clutter and prevent our phones from prioritizing slow or insecure networks over better connections. Remember that many devices default to the network with the strongest signal, even if it's not the most secure or fastest option available at that moment.
Best practices for using WiFi networks outside the home
Beyond disabling automatic connections, it's advisable to adopt a few basic habits when using Wi-Fi outside your trusted environment . This isn't about living in paranoia, but rather applying common sense and a bit of discipline to drastically reduce the likelihood of an attack.
Whenever possible, it's preferable to use mobile data (2G, 3G, 4G, or 5G) rather than connecting to a public Wi-Fi network , especially if you're going to access online banking, work email, social media, or any service that handles sensitive data. Mobile networks, even with their vulnerabilities, generally offer a higher level of security against local traffic interception attacks.
If you have no choice but to use public Wi-Fi, it's crucial to verify that the connection is encrypted with HTTPS . You can look for the padlock icon in your browser and, before clicking on a link, hover your mouse over it (on computers) or carefully review the URL to ensure you're clicking on the legitimate site and not a fraudulent copy.
For added security, using a VPN (Virtual Private Network) is highly recommended . A VPN creates an encrypted "tunnel" between your device and the provider's server, so even if someone intercepts traffic on your local Wi-Fi network, they will only see meaningless encrypted information. These services have become extremely popular, and there are both free and paid options available, with varying levels of quality.
Furthermore, we should avoid sending particularly sensitive information if we are connected to a network we don't trust . Banking transactions, password changes, dealings with government agencies, or sending private documents should be reserved, whenever possible, for secure and trusted connections, whether it's our home network or a mobile network.
Protect your home router and limit who can connect
The other side of the coin is home Wi-Fi connections, where we also need to be careful about security . A poorly configured router can allow neighbors, intruders, or attackers to infiltrate our network, consume our bandwidth, or even access IoT devices such as IP cameras or voice assistants.
Some basic measures to strengthen router security are almost textbook : use long and strong Wi-Fi passwords, change the network name (SSID) so it doesn't reveal the router model or provider, change the password to access the administration panel, and enable modern encryption protocols like WPA3 (if available) or, failing that, WPA2 with a strong key. It's also a good idea to be aware of any Wi-Fi theft and block those individuals.
If we want to go a step further, we can restrict access even more by filtering by MAC addresses . Each device (mobile phone, laptop, tablet, smart TV, etc.) has a unique MAC address assigned by the manufacturer, consisting of six pairs of alphanumeric characters separated by colons, something like YY:BB:CC:DD:EE:FF.
The router's settings panel usually has an "Access Control" section , or something similar, within the advanced or security settings. Here, you can create a whitelist of allowed devices' MAC addresses or a blacklist of those you want to block. If you configure a whitelist, only devices whose MAC addresses you've added will be able to connect, even if someone knows the password.
To find the MAC address of your device, simply check its network settings . On iOS, it's usually found in Settings > Wi-Fi > tapping the active network, under the "Wi-Fi Address" field. On Android, it typically appears in Settings > Network & Internet > Internet > your network, within the network information or advanced details section.
Private MAC addresses and their effects on access control
In recent years, both iOS and Android have incorporated privacy features that use random MAC addresses instead of the device's actual MAC address for each Wi-Fi network. The goal is to prevent third parties from tracking our movements simply by following our actual MAC address as we move between different access points.
This means that, for each Wi-Fi network, the mobile device generates a different "private" MAC address . This address remains constant for that specific network, but it doesn't match the device's physical MAC address. This is very positive for privacy, but it complicates MAC filtering on the router, because we could be adding the private MAC address to the whitelist instead of the actual one.
If we add the private MAC address generated by the mobile device to our home network in the router , everything will work as long as we don't change certain device settings. However, if we perform a factory reset, change mobile devices, or disable/reconfigure the random MAC address feature, that address will likely change, and we'll need to update the router's whitelist for the device to reconnect.
This is important to keep in mind when combining MAC address filtering with advanced privacy features . Depending on how complex we want to be, we can choose to disable MAC address randomization only on our home network (keeping it active on public networks) or, alternatively, forgo MAC address filtering altogether and focus on other security layers such as strong passwords, firmware updates, and network segmentation.
In any case, if we notice that a trusted device can suddenly no longer connect to our WiFi despite using the correct password, it's a good idea to check both the router's MAC filter and the private MAC address settings on the device itself, because the problem is usually there.
Extra measures for a more cybersecure digital life
Beyond Wi-Fi, cybersecurity relies on a set of best practices that should be applied consistently . A well-protected home network is of little use if we then fall for a phishing email, download a malicious app, or always use the same weak password for all services.
Automatically updating device operating systems, applications, and firmware is crucial because many patches correct critical vulnerabilities that attackers know about and exploit. Configuring automatic updates reduces the risk of becoming outdated and exposed to documented techniques.
It's also advisable to use a password manager and enable two-step verification (2FA) whenever possible . This way, even if someone steals your credentials through a compromised Wi-Fi network, it will be much harder for them to access your accounts if they need a second factor (temporary code, physical key, authenticator app, etc.).
Finally, it's advisable to get some basic training on threats like malware, ransomware, phishing, smishing, and vishing . Understanding how these attacks work helps us recognize warning signs: urgent messages asking for data, suspicious links, unexpected attachments, or calls from banks and organizations trying to pressure us into acting quickly.
Adopting these habits—checking your Wi-Fi, using a VPN, updating software, monitoring passwords, and being healthily suspicious of what you receive online— significantly reduces your attack surface. It's not about being 100% protected, which is impossible, but about making it as difficult as possible for cybercriminals and reacting quickly to any suspicious activity.
Controlling which networks our mobile phone connects to, disabling automatic connections, deleting WiFi we no longer use, and strengthening router security are simple actions that make a huge difference: we go from running on "autopilot" to being the ones who decide when, how, and with whom our data is shared, minimizing the risk of a simple free connection turning into a headache.
