Here’s an easy way to visualize a man-in-the-middle attack. Imagine you visit an ATM and someone eyes your card details by peering over your shoulders. You’re not aware that they are standing behind you. They memorize your details, leave, and cash out using your card info from another location later. They could also install a device between the ATM and the host to steal your details when you swipe your card, without you knowing about it! That’s a classic MitM attack in action. Another example is a stranger eavesdropping on a chat with your friend and using your sensitive info against you two.
MitM attacks aren’t just physical, they occur a lot in the cloud and cyber security worlds. In this guide, we’re going to explain how to prevent MitM attacks and what you can do about them.
What are Man-in-the-Middle Attacks?
A man-in-the-middle (MitM) attack happens when a threat actor intercepts communication between two parties who are unaware of them. The hacker eavesdrops on their conversation and is capable of stealing sensitive data like financial information, login credentials, and any other confidential details exchanged between them.
Most man-in-the-middle (MitM) attacks take place across unsecured public WiFi networks via phishing and web spoofing.
Why Preventing Man-in-the-Middle Attacks Is Important?
In an MitM attack, you won't be aware that the attacker has invaded your presence. It's silent and the criminal's goal is to lurk and steal as much as info by eavesdropping on your convo with other parties and agents.
MitM attacks are dangerous because they can target any person, business, organization, and asset. The motive extends beyond financial gain and if you're not careful, you could risk losing millions of records from a single data breach.
Industries that are constantly targeted by MitM attacks include banking sectors, fintech and healthcare companies, and industrial IoT verticals. Manufacturing warehousehouses, power systems, and critical infrastructures are not safe either.
According to the SCORE and the SBA report, MitM attacks account for 43% of cyber attacks around the world! Small and midsize businesses are their biggest and most frequent targets.
How Man-in-the-Middle (MitM) Attacks Work
Here is what a typical Man-in-the-Middle (MitM) attack looks like:
- Person A will send a message to Person B
- The "Man-in-the-middle" will intercept the message without either person A or B knowing
- He/she may change the message, its contents, or delete the message altogether without them finding a trace of their activity nor knowing about it
In short, a Man-in-the-Middle Attack will exploit network, web, and browser-based vulnerabilities to intercept or divert legit traffic. It can steal info from victims and even take advantage of weaknesses in security protocols.
Warning Signs of a Potential MitM Attack
Here are some signs that tell you if you are a victim of an MitM attack:
Browser Certificate Warnings
When you visit a website, your browser checks the security certificate. If something's wrong, it tells you. A certificate warning means the site's identity doesn't match what's expected or the certificate expired.
Legitimate sites don't produce certificate errors. If you suddenly see these warnings on a site you visit regularly, someone could be intercepting your connection. They're using a fake certificate to sit between you and the real server. A certificate mismatch or invalid certificate error is a red flag that traffic is being intercepted.
Strange URLs
Attackers use URLs that mimic legitimate websites. The domain might be spelled slightly differently, use a different extension, or have an extra character. Your-bank.com instead of yourbank.com. Amaz0n.com with a zero instead of an o. These tiny differences are easy to miss if you're not paying attention.
Check the URL in the address bar before you log in or enter sensitive information. Phishing often works with MitM attacks—the attacker shows you a fake login page while also intercepting your real traffic. URLs that are close but not quite right often indicate you're being rerouted through an attacker's server.
Unexpected Disconnections from Services
Your email logs you out randomly. Your banking app disconnects mid-session. Your messaging app drops its connection repeatedly. These disconnections happen without explanation and sometimes come back just as suddenly.
An attacker intercepting your traffic might force these disconnections to reset the connection through their server. Repeated forced logouts, especially across multiple services on the same network, suggest your session is being hijacked and rerouted. The attacker needs to reset connections to stay undetected.
Your Device Won't Connect to Secure Websites
Websites that normally load with HTTPS (the padlock icon) suddenly load as HTTP (no padlock). Or they fail to load entirely. Your browser might show an error about not being able to establish a secure connection.
Some networks downgrade HTTPS to HTTP to reduce load on their systems. But MitM attackers do this intentionally to remove encryption. If a site you know has HTTPS suddenly shows no padlock, or if you can't establish any secure connection to it, your traffic might be intercepted.
Unencrypted WiFi in Risky Locations
You connect to WiFi from a coffee shop, airport, library, or hotel that doesn't use a password. These networks broadcast their signal openly, meaning anyone nearby can monitor the traffic. An attacker doesn't even need to be at the same location—they just need to be on the same network.
Public WiFi from unsecured locations is the easiest place for MitM attacks to happen. An attacker sets up nearby, connects to the same network, and monitors all traffic. The risk is even higher in crowded public spaces where you don't know who's sitting around you or what devices they're running.
Multiple Similar WiFi Networks
You see several networks with nearly identical names. "AirportWiFi" and "AirportWifi" (capital W). "CoffeeShop_Guest" and "CoffeeShop_Guest5G". An attacker creates a fake network with a name almost identical to the real one.
When you connect to the wrong network by mistake, the attacker has direct access to everything you do. They don't need to intercept—you're sending data directly to their device.
These duplicate network names are a common setup for MitM attacks because users connect without checking carefully.
Strange DNS Behavior
Your DNS queries get redirected to unexpected servers. Websites load but seem different—different ads, different layout, extra pop-ups. Or websites don't load at all and show error pages instead.
DNS hijacking is a form of MitM attack where the attacker intercepts your DNS requests and sends you to fake websites or blocks sites entirely. If a site you know well loads with a different appearance or layout, someone could be intercepting your DNS queries and serving you a modified version.
Certificate Pinning Failures
Apps that normally load without issues suddenly show certificate errors. Your banking app won't connect. Your email client displays a security warning. These warnings appear even though you're using the app you always use.
Some apps use certificate pinning—they only trust specific certificates from their servers. When an attacker intercepts the connection with a fake certificate, the app refuses to connect because the certificate doesn't match what it expects. Certificate errors on apps you use regularly indicate interception.
Man-in-the-Middle Proxy Alerts
Your device shows a message about a proxy server that you didn't set up. Your network settings show traffic is routing through an unknown proxy. Your browser starts asking about proxy authentication even though you never configured one.
Attackers set up proxy servers to intercept traffic. If you see proxy settings you don't recognize or prompts for proxy authentication appearing unexpectedly, your traffic is being routed through an attacker's device.
Session Tokens and Login Cookies Getting Stolen
You stay logged into services, but then suddenly get logged out. When you log back in, you see login attempts from locations you weren't in. Your account settings show devices you don't own.
An attacker who intercepts your traffic can steal your session cookies or login tokens. They use these tokens to access your account without needing your password. If you see login activity from unfamiliar locations or devices, someone captured your session credentials.
Downgraded Encryption or SSL/TLS Issues
Websites that normally use strong encryption suddenly show weak encryption warnings. Your browser displays messages about outdated security protocols. Connections use older, less secure versions of HTTPS.
MitM attackers try to downgrade your connection to older, weaker encryption standards that are easier to break. If you see warnings about outdated SSL/TLS versions or weak encryption, your connection is being intercepted and downgraded.
DNS Cache Poisoning Signs
Websites redirect to the wrong places. You click a link to your bank but end up on a fake site. Domain name lookups take longer than normal or return unexpected IP addresses.
An attacker poisons your DNS cache by feeding your device fake IP addresses for real websites. You think you're connecting to the real site, but you're actually connecting to the attacker's fake version. Redirects to wrong sites and slow DNS lookups indicate cache poisoning.
Device Battery Drains Unusually Fast
Your phone or laptop battery depletes much faster than normal even though you're not using it heavily. Your device gets hot without any apps running in the foreground. Background processes consume data you didn't authorize.
An attacker intercepting your traffic might be running logging tools or data exfiltration processes on the same network. These processes consume power and generate heat. Unexplained battery drain and overheating on specific networks suggest background traffic interception.
Email or Message Routing Changes
Emails take much longer to arrive than usual. Messages you send don't reach their destination. Confirmations come from slightly different email addresses than normal. Communication with contacts becomes unreliable or delayed.
An attacker intercepting your email or messaging traffic might be delaying, modifying, or rerouting messages. If specific communication channels become unreliable only on certain networks, someone could be intercepting that traffic.
Network Traffic Anomalies
Your data usage increases unexpectedly without any new apps or activities. Network speed slows significantly on a particular connection. Bandwidth throttling happens only on specific networks.
When an attacker intercepts traffic, they're copying it, logging it, or analyzing it. This creates additional data flows and can slow your connection. Sudden increases in data usage or speed drops on certain networks indicate extra processing happening to your traffic.
Login Credentials Stop Working Temporarily
You try to log into a service and it fails, even though you know your password is correct. After a few minutes, you can log in normally. This happens repeatedly on the same network.
An attacker might be intercepting and modifying your login attempts to intercept the credentials. They could be delaying your actual login attempt while they capture what you send. Repeated failed logins followed by success suggests someone is tampering with your authentication traffic.
Best Practices to Prevent MitM Attacks
Now here are some of the best MitM attack prevention
1. Update your WFH Policies and Secure Home WiFi Routers
If your employees work from home, then one of the best things you can do is to secure WFH and corporate networks. Use good WiFi router software (firmware) and set it up so that it updates automatically. Also, make sure your router's security settings are strong and adhering to WPA3 standards minimum. Encourage your employees to connect to the internet with VPN if they are traveling. Encrypted traffic is difficult to modify or intercept, that's why.
2. Use End-to-End Encryption
Ask your employees to turn on end-to-end encryption for emails and communication channels. Some apps do this on their own in the background like Whatsapp and Telegram, but not all apps are configured like that. They can also use scanning and QR codes with their software and phones to get end-to-end encryption. Do some research and get this set up if your company uses private apps.
3. Install Patches and Antivirus Software
This might seem like a beginner move but it's something most employees and companies miss. Don't be naive, thinking attackers assume you have done this. You'd be surprised how many organizations fail basic cyber hygiene checks. Install and patch your security software without fail. Also, strengthen your endpoint security measure by installing the strongest endpoint protection suite.
4. Use a Password Manager and Set Strong Passwords
Don't use passwords that are easy to guess or crack like "Muffin@Paleo123". Don't use your DOB, phone numbers, or personal details in your passwords. Use a mix of letters, numbers, and symbols, and make sure the length is good. Don't recycle or reuse the same password for every web page, app, and service. You should use a different password for everything. Use a good password manager to keep track of your passwords across services. Update your password management policies as well in your company and ask your employees to change their passwords every month or more regularly.
5. Apply Multi-factor Authentication (MFA)
Use MFA on online services and devices to defend against emerging threats. It will serve as your best defense. You can also try using authentication apps and set up to receive OTPs on devices as an extra layer of security.
6. Connect to Secure Website Only
Notice the padlock icon on the left of your browser URL? Yeah, that tells you if a site is secure. Don't forget the "https://" prefix either. Tell your employees to check for these signs before they visit websites. They can also install free browser plugins that can do website audits/checks before allowing them to visit, so that they follow this rule automatically.
There are many web filtering protocols that prevent employees from accessing non-HTTPS sites. SentinelOne has a browser extension and a Firewall control module that can help with this. You can access its web filtering capabilities as a part of its comprehensive endpoint and network security features via its platform.
7. Monitor Network Traffic for Unusual Activity
Your employees might not notice suspicious data flows, but your security team should. Set up network monitoring tools to watch for unexpected outbound connections or traffic spikes during odd hours. When you see unusual patterns, investigate them quickly. Attackers often leave traces in network logs before or after a successful MitM attack.
Tools that log and analyze traffic can catch these signs. You don't need enterprise-grade software for this—most routers have basic logging built in. Check the logs weekly and flag anything out of place. Also, train your employees and make them be aware of the latest social engineering schemes. They should be able to spot phishing emails and signs of smishing and vishing. Teach them to not engage with unknown adversaries. Verify who they talk to online and not give away sensitive info by blindly trusting strangers.
8. Disable Older Network Protocols
Your network probably still supports older protocols like SSL 3.0 and TLS 1.0, which have known vulnerabilities. Attackers exploit these outdated standards to intercept traffic. Update your network and device settings to use TLS 1.2 or higher.
Tell your IT team to turn off legacy protocols on servers, routers, and endpoints. If old protocols stay enabled, you're leaving a door open. This might break compatibility with very old devices or software, but the security gain outweighs that risk. Check what your employees actually need to connect to, then disable the rest.
9. Use SSL/TLS Certificates and Verify Them
Certificates prove that websites and services are what they claim to be. Your company should install legitimate SSL/TLS certificates on any internal or external-facing services. More importantly, train staff to check if certificates are valid.
Browsers show certificate details when you click the padlock icon. If a certificate doesn't match the domain or has expired, don't proceed. Attackers sometimes use expired or self-signed certificates to intercept traffic. A quick verification habit stops most MitM attempts that rely on fake certificates. Make this part of your security onboarding for new hires.
10. Segment Your Network and Restrict Access
Not everyone in your company needs access to every system. Break your network into separate zones—finance, HR, development, guest WiFi—each with its own security rules. If an attacker compromises one segment, they can't automatically reach the rest.
Use firewalls and access controls to limit what devices and users can connect where. An employee in accounting doesn't need to reach your server infrastructure. This approach also makes it harder for attackers to move laterally after gaining initial access. Start by separating sensitive data from general use areas, then refine based on your company's actual roles and needs.
How SentinelOne Helps Prevent Man-in-the-Middle Attacks?
SentinelOne doesn’t have a dedicated product to block Man-in-the-Middle attacks exclusively, but it does provide a mix of security offerings that help you combat and defend against these threats. For example, you can use Singularity™ Endpoint to get AI-powered autonomous endpoint protection for your networks, identities, users, and devices.
Singularity™ Mobile will give you on device, adaptive and real-time defenses to fight the rising tide of mobile threats. It can eliminate risks from jailbroken and rooted devices. It can help you defend against man-in-the-middle (MitM) attacks, including rogue, wireless and secure communication tampering. You can block phishing URLs and behaviorally detect emerging phishing techniques. Get alerts about suspicious links in texts, messaging apps, email, and social media. Prevent credential theft and account compromise before users engage.
Singularity™ XDR can take it up a notch by providing better security coverage. It can stop threats like ransomware and provides a unified security platform for addressing data siloes. You can ingest and normalize data from any source and correlate across any attack surface. It helps you understand the full context of attacks.
SentinelOne uses multiple threat detection engines that can give you better visibility of your infrastructure. You can monitor data flows, spot dormant/inactive accounts, analyze network traffic and user behaviors. Here’s what you should know about them:
- SentinelOne's static AI engine can scan files before execution and identify patterns of malicious intent. It can classify benign files too.
- Its behavioral AI engine can track relationships in real-time and guard against exploits and fileless malware attacks.
- There are engines that can do holistic root cause and blast radius analysis.
- The Application Control Engine can ensure container image security.
- STAR Rules Engine is a rules-based engine which enables users to transform queries of cloud workload telemetry into automated threat hunting rules.
- SentinelOne Cloud Threat Intelligence Engine is a rules-based reputation engine which uses signatures to detect known malware.
Prompt Security by SentinelOne can block unauthorized agentic AI actions and malicious prompts. It prevents prompt injection and denial wallet/service attacks, and will instantly send alerts regarding shadow AI usage. Finally, Purple AI is the world’s most advanced Gen AI cybersecurity analyst that can help you out. It generates the best security insights and helps you get the most out of your security investments. You can get access to all these integrated security features through SentinelOne’s Singularity™ Platform.
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Learn MoreConclusion
Now that you know how MitM attacks work and how to prevent MitM attacks, you’ll be more confident about applying the best security protocols. Use the right integrated security stack for your organization and keep everyone in the loop. Educate your employees about these threats and test to see if they know what to do to not get intercepted. With SentinelOne by your side, you can guard against these threats and prevent adversaries from snooping in on your communications.
FAQs
A Man-in-the-Middle attack happens when an attacker positions themselves between you and the server you're trying to reach. They intercept the data you send and receive, reading or modifying it without your knowledge. The attacker can steal sensitive information like passwords, credit card numbers, and login credentials. They basically act as a go-between, pretending to be the legitimate service while capturing everything that passes through.
When you're on public Wi-Fi, avoid accessing sensitive information if you can. If you have to use it, make sure you're using a VPN to encrypt your connection. Check that websites use HTTPS and have a valid SSL certificate before entering any personal data. Don't trust networks with generic names that don't require passwords. Turn off auto-connect features on your device, and disable file sharing. You should also avoid banking or shopping on public networks whenever possible.
Use a VPN for all your internet traffic, especially on untrusted networks. Enable HTTPS and verify SSL certificates on websites you visit. Keep your browser and operating system updated with the latest security patches. Use strong passwords and enable multi-factor authentication on all your accounts. Monitor your network traffic for unusual activity or unfamiliar devices. If you fail to do these things, you're leaving yourself exposed. Install antivirus and anti-malware tools to catch threats before they spread.
Implement network segmentation to isolate sensitive systems from general traffic. Deploy a Web Application Firewall to inspect and block suspicious traffic. Use certificate pinning to verify legitimate servers. Monitor all network connections with intrusion detection systems. Require VPNs for remote workers and enforce strong authentication protocols. Conduct regular security audits to find gaps in your defenses. Make sure your teams understand how MitM attacks work and can spot warning signs on their devices.
Multi-factor authentication adds another layer of security, but it doesn't stop MitM attacks completely. An attacker who intercepts your traffic can potentially capture your username and password, but they'll hit a wall when the second authentication factor kicks in. If they don't have your phone or authenticator app, they can't get past MFA. It makes attacks much harder and time-consuming, so attackers usually move on to easier targets. You should use it as part of your overall security plan.
Endpoint protection tools can detect some MitM activity, but they're not a complete defense on their own. They will catch malicious traffic patterns and suspicious certificate installations on your device. A good endpoint tool monitors network connections and flags unusual behavior. However, if the attacker is positioned between you and the server, your device alone can't see that. You need to combine endpoint protection with network-level defenses like VPNs and firewalls for real protection.
If you detect a MitM attack, disconnect from the network immediately. Don't continue accessing sensitive accounts or sending personal data. Change all your passwords from a different, secure device that you know hasn't been compromised. Contact your IT team or network administrator right away. Check your accounts for unauthorized access or suspicious activity. If you have to, file a report with your security team. Review logs to see what data was accessed, and notify anyone who might have been affected by the breach.
