I'm sure it happens to you every day: you go to a restaurant, want to see the menu, and without thinking twice, you take out your phone to scan the QR code on the table. It's become so commonplace that it's part of our routine, from paying for parking to downloading an app. However, that same blind trust in technology is precisely the vulnerability that cybercriminals are exploiting to slip their scams past us.
This is where quishing comes in, a term that combines "QR" and "phishing." Essentially, it's a deceptive technique where malicious actors use these small black and white squares to redirect us to fraudulent websites or trick us into downloading malware. Because the content of a QR code is invisible to the human eye until it's processed, it becomes the perfect tool to bypass security filters that would normally detect a suspicious link in an email.
How exactly does quishing work?
The process is very similar to traditional phishing, but with a tactical twist. Instead of sending you a text link that you can analyze before clicking, the attacker presents you with an image. When the device scans the code, it extracts the URL and opens the browser. The real danger lies in the fact that these attacks often use social engineering , playing on our emotions, creating a false sense of urgency, or promising incredible rewards to get us to act impulsively.
There are several attack vectors. One of the most common is the overlaid QR code , where the scammer places a sticker with their own code over the original in public places, such as parking meters or bus signs. There are also digital attacks, where the code arrives disguised in an email, SMS, or even a PDF, tricking you into thinking you need to update your bank details or process a non-existent traffic fine.
The hidden dangers behind scanning
Depending on the attacker's intentions, the outcome of scanning a fraudulent QR code can vary. In many cases, you'll end up on a phishing website that perfectly mimics your bank's or an official entity's page to steal your username and password. In other cases, the code may trigger the automatic download of a Trojan horse or spyware app that takes control of your phone.
There's a more technical and dangerous variant called QRLJacking . Here, the hacker clones a legitimate login code (very common in banking apps or modern services) and redirects it to their own server. If the victim scans that code and doesn't have two-step verification enabled, the attacker can directly access the account without needing the password, since the scan acts as the access key.
Why are we so vulnerable to this scam?
The main reason is that quishing breaks the corporate security chain. Imagine you receive a malicious email on your work computer; the company's antivirus will likely block it. But if the email contains a QR code, you'll scan it with your personal mobile phone , which typically doesn't have the same protections or follow the office's security policies. This creates a blind spot where the threat goes undetected.
Furthermore, mobile devices are often the weak link. While we are more cautious on PCs, we tend to trust smartphones more and ignore red flags like spelling mistakes or strange URLs. This combination of the ubiquity of QR codes and less vigilance on mobile devices creates the ideal scenario for cybercriminals.
Most common types of scams in the real world
- Parking fraud and fines: They place stickers on parking meters or leave notices on the windshield with a QR code to pay with a discount, thus emptying the victim's account.
- Deceptions in the hospitality industry: Fake QR codes on restaurant tables that take you to websites where they ask for your card details to participate in fake raffles.
- Cryptocurrency gambling: Codes that promise quick investments or Bitcoin prizes, but actually steal your digital wallet keys.
- Messaging spoofing: DHL or Correos emails that ask you to scan a code to solve a problem with the delivery of a package.
Strategies to avoid falling into the trap
The first golden rule is not to scan just anything you find. If you see a QR code that looks like a sticker stuck on top of another one, or has raised or poorly cut edges, be immediately suspicious. In restaurants, if you have any doubts, it's best to ask the waiter or request a paper menu to avoid unpleasant surprises.
On a technical level, it's essential to configure your phone to display the destination URL before opening it. Take a moment to read it: if the domain is "parking-madrid-pagos.com" instead of "madrid.es", it's a scam. Also, avoid downloading apps that require a QR code; always go directly to the official App Store or Google Play.
Advanced defenses for businesses and users
For those who manage organizations, simply giving a presentation isn't enough. It's necessary to implement image analysis engines in email filters that can decode QR codes in real time and compare them against threat databases. Using sandboxing, which involves running the link in an isolated environment before it reaches the user, is one of the most effective measures currently available.
For the average user, the most powerful tool remains two-factor authentication (MFA) . Even if a scammer manages to steal your credentials through a quishing site, they won't be able to access your account without the temporary code sent to your mobile phone. Keeping your operating system updated is also key, as many attacks exploit browser security vulnerabilities that have already been patched.
What to do if you've already taken the bait
If you realize you've scanned malicious code, act quickly. If you only opened the website, close the tab, clear your browsing history and cookies, and run an antivirus scan. But if you entered personal information, contact your bank immediately to block your cards and change all your passwords from a clean device.
If you've installed a suspicious app, uninstall it and check what permissions you granted it. In extreme situations, where you believe the malware has compromised the entire system, the safest course of action is to restore your phone to factory settings to remove any trace of the spyware and report the incident to the National Police.
Maintaining a skeptical attitude toward QR codes that appear out of nowhere and always verifying the website domain before entering any information is the best defense. Combining human caution with tools like two-step verification and an up-to-date operating system drastically reduces the chances of a simple scan turning into a financial or privacy nightmare.