In today’s rapidly evolving cyber threat landscape, attackers are using increasingly sophisticated tactics to bypass traditional email security tools. One of the most alarming trends is the rise of QR code phishing attacks, where malicious QR codes are embedded in email attachments (especially PDFs) to trick users into scanning them with mobile devices. These scams often lead to phishing sites, credential theft, and mobile device exploitation. In this blog, we’ll break down how QR code-based email scams work, why they’re so effective, and how organizations and individuals can protect themselves from this growing form of mobile-targeted cyberattack.
What Are QR Codes and Why Are They a Threat?
Quick Response (QR) codes are two-dimensional barcodes that, when scanned by a smartphone or tablet, direct users to various digital destinations such as websites, apps, contact information, and more. Their convenience and familiarity have led to widespread use in both personal and professional environments, making them a prime target for attackers. QR code hacking tactics continue to evolve, as we’ve outlined in a related post on common exploitation methods. Unfortunately, this same ease of use has also made QR codes an increasingly attractive tool for cybercriminals. Scanning a malicious QR code can direct users to phishing sites, fake login pages, or even trigger unwanted downloads that compromise devices and networks. The risk is increased because QR codes are inherently opaque: users cannot see or verify the link behind the code before scanning.
How Attackers Are Using PDFs with Customized QR Codes to Bypass Defenses
Traditionally, email security solutions rely on detecting harmful links, attachments, and malicious payloads within the email body. However, attackers have started bypassing these filters through a simple yet clever technique: embedding QR codes inside PDF attachments.
Here’s how it works:
Personalized Campaigns
- Attackers craft PDF files containing QR codes that are customized with the recipient’s company branding, name, or role. This increases user trust, making the PDF and its embedded QR code appear legitimate. Here is an example email that one of our iCorps employees received, and their username has been redacted for privacy:
Bypassing Filters
- Most email security filters and sandboxing engines focus on detecting suspicious URLs or executables. QR codes, as images, often aren’t parsed or checked for harmful destinations, especially when embedded in PDFs.
Mobile Device Exploitation
- As users often access emails on their phones, they may be more likely to scan a QR code with the same device, bypassing desktop protection layers.
Credential Harvesting and Token Theft
- Once scanned, users are directed to phishing sites mimicking familiar login portals. Victims might enter their credentials, giving attackers access to corporate accounts, or even approve OAuth token requests, enabling deep access without passwords.
The seamlessness, personalization, and psychological manipulation of these campaigns make them highly effective and dangerous.
The Double-Edged Sword of Mobile Convenience
Many organizations have strengthened desktop email security with solid solutions, but the increase in mobile device usage introduces new challenges. Employees, eager to fix issues or respond swiftly, often use their mobile camera to scan a QR code without hesitation. This switch from the relatively secure world of a desktop to the personal, less protected mobile environment gives attackers a significant advantage.
Education: The First and Best Line of Defense
While security tools are evolving to identify suspicious QR codes and malicious PDFs, technological solutions will always be a step behind novel attack techniques. That’s why end-user education is critical—not just for spotting QR scams, but for recognizing the full spectrum of email-based threats. For broader awareness, explore our guide to the five most common phishing attacks.
🧠Think Before You Scan
- Employees should be trained to treat QR codes with the same skepticism as email links, especially those delivered via unsolicited or unexpected PDFs.
🕵️Verify Source and Intent
- Before scanning, users should confirm the legitimacy of the sender and the message’s context. If something seems off, it probably is.
🌐Hybrid Work Awareness
- Remind staff that the threats present on corporate networks extend to mobile and personal devices as well.
📣Routine Awareness Campaigns
- Incorporate QR code threats into regular cybersecurity awareness sessions and phishing simulation exercises.
Tips for Safer QR Code Use (Business and Personal)
For small and mid-sized business owners, protecting your company from QR code phishing doesn’t have to be expensive or complicated. Simple security habits, like training employees to recognize suspicious QR codes, can go a long way in preventing credential theft, data breaches, and email scams. By encouraging smarter behavior around QR code use, you can reduce risk without adding costly tools or infrastructure.
🔒 Avoid Scanning QR Codes from Unknown Sources
- Never scan QR codes included in emails or messages from senders you don’t recognize or trust. These are often used to lure you into phishing sites or malware traps.
🧠 Watch for Social Engineering Tactics
- Be alert to red flags like urgent language, strange branding, or generic greetings. These are classic signs of manipulation used in QR-based phishing attempts.
🔍 Verify URLs Before Entering Credentials
- If scanning a QR code leads to a login page, double-check the URL in your browser. It’s safer to manually navigate to known websites rather than relying on redirected links.
📱 Keep Devices and Apps Updated
- Regularly update your mobile operating system and apps. Security patches help close vulnerabilities that attackers might exploit after you scan a malicious QR code.
🛡️ Explore QR Code Scanning Protection Tools
- Consider deploying tools that analyze QR codes in email attachments at the security gateway. These are still evolving, but can offer added defense layers against newer threats.
Frequently Asked Questions About QR Code Phishing
❓What is QR code phishing (squishing)?
- QR code phishing, also known as quishing, is a cyberattack in which a malicious QR code directs the user to a fake website. These scams often trick users into entering login credentials or downloading malware, especially when delivered via email attachments or printed materials.
❓Can email filters detect QR code threats?
- Most traditional email filters and security tools struggle to detect QR-based threats, especially when QR codes are embedded as images in PDF attachments. Since these codes aren't text-based URLs, they often bypass standard link-scanning filters.
❓Why are mobile devices especially at risk?
- Mobile users are more likely to scan QR codes impulsively and without verifying the source. Mobile devices often lack enterprise-grade protection, making it easier for attackers to exploit them through phishing links, credential harvesting, or malicious apps.
❓How can I safely verify a QR code before scanning?
- To verify a QR code, use a scanning app that shows the destination URL before opening it. Avoid scanning codes in emails or PDFs unless you’re sure they come from a trusted source. When in doubt, navigate directly to the intended website instead of using the code.
❓What should my business do if an employee scans a malicious QR code?
- If a suspicious QR code is scanned, your IT or security team should act quickly: change any compromised passwords, revoke third-party app access (OAuth tokens), and monitor for suspicious account activity. Ongoing employee training can help prevent future incidents.
Protect Your Organization from Emerging Threats
As QR code-based attacks become more sophisticated and personalized, the responsibility to defend against them now rests on both users and organizations. A well-informed user is far less likely to become the next victim, which is why education remains the single most effective security control in this new era of digital threats.
“The weakest link in security is, and always has been, the human. Equip your people with knowledge—they’re your last, best line of defense.”
Contact our cybersecurity experts today to schedule a security audit or awareness training session.