PDFs: The Rising Threat Hiding in Plain Sight – Are You at Risk?
PDFs, once considered a safe and reliable format for documents, are increasingly becoming a favorite tool for cybercriminals. Several recent reports highlight a surge in PDF-based attacks, with attackers using sophisticated techniques to bypass security measures and exploit user trust. This trend demands a critical re-evaluation of how we handle PDFs across all devices, from PCs to smartphones.
Microsoft issued a warning regarding malicious PDF attachments being used in attacks, just weeks after alerting Windows users to the growing threat. These attacks often involve embedded DoubleClick URLs redirecting users to fake DocuSign pages. A new campaign spotted by TrustWave SpiderLabs uses a fake payment SWIFT copy to deliver RemcosRAT, employing steganography to hide the malicious payload within seemingly harmless images hosted on archive.org.
According to Cybersecurity News, these attacks often originate from phishing emails with PDF attachments containing malicious links. This multi-stage infection process is designed to deliver RemcosRAT, a malware capable of remotely controlling infected systems. The core issue is the user's perception of PDFs as safe, unlike Office documents, leading to a false sense of security.
Check Point Research reports that 22% of all malicious email attachments are now PDFs, signifying a significant increase. With 68% of cyberattacks still starting with email, the elevated use of malicious PDFs represents a dangerous trend. The format's widespread use in business communication makes it an attractive vector for attackers.
The threat is not limited to PCs; mobile devices are also at risk. Zimperium has observed a surge in PDF attacks targeting smartphones, particularly via SMS. Attackers are leveraging well-known brands to manipulate user trust, making them more likely to click on malicious links embedded within the PDF. These attacks exploit the fact that users are accustomed to trusting PDFs, and many defense mechanisms may not thoroughly inspect them for embedded threats.
Zimperium's Mobile Threat Report 2025 highlights that SMS threats now constitute over two-thirds of observed attack attempts. A PDF attached to an SMS represents a double whammy, bypassing security scans and capitalizing on user trust in familiar brands.
Key takeaways: Pay close attention to email senders and avoid opening PDFs from unknown sources. Do not open PDFs that appear to be copies of SWIFT payments. Examine carefully SMS that appear to be from brands you know, they maybe fake. It's crucial to question PDFs regardless of source or content. Be very careful of any PDF that may come from your bank if it is an unexpected email. Never open a PDF that does not seem right. There are ways for the end user to test the safety of a URL by copying and pasting, not clicking, the URL into a safety checker.
The evolution of obfuscation tactics and the rise in smishing kits highlight the need for increased vigilance. The old days of trusting a PDF are gone, and experts warn that all PDFs pose a potential threat. By understanding the nature of the threat, you can be much more careful when opening a suspect PDF.
Bottom line: Given the rise of PDF-based attacks, users need to treat every PDF with caution. Are you prepared to adjust your habits to protect yourself from this growing threat? Leave your thoughts and share your experiences in the comments below.
