The first computer virus arrived over 50 years ago. Though it was a harmless piece of software designed to demonstrate potential vulnerabilities in computer systems, it would be a grim predictor of things to come.

Now, malware is a multi-billion dollar industry. In early May, a ransomware attack forced the historic Lincoln College to shutter its doors permanently. And that’s only one newsworthy example.

But despite these high stakes, many underestimate the risk malware poses. The PDF virus is a good example. To understand the threat a malicious PDF file can present, let’s take a look at PDFs in general, and how they can install malware on a system.

What’s the Purpose of a PDF Document?

PDF files are one of the most common file formats used for sending documents. Everyone from private citizens to schools and hospitals uses them. Some go so far as to program C# HTML to PDF converters to make PDFs easier to produce in quantity.

PDfs are useful because they’re not easy to edit. Even with specialized software, you usually can’t open up a PDF and make any changes you like. This makes them useful for contracts, bank statements, and other important documents that need to be signed and sent.

But the “fill and sign” abilities that make PDFs so useful are also where they can pose a threat. The same scripts that make those capabilities possible can hide malicious code. And further, multimedia components and hyperlinks in the body of a PDF can likewise hide malware.

How Does a PDF Virus Work?

PDFs were long thought to be a safe file format, immune to hidden malware. That conception is partly why they’re such a threat. People will be wary of suspicious websites but tend to trust that a PDF is harmless.

In reality, there are multiple ways to hide malware in a PDF.

The “fill and sign” feature is a major one. This function can be used to carry out phishing schemes or install malicious software onto your computer.

Multimedia components of a PDF like video or audio features can be used to hide Trojan viruses. The media itself will play as normal, helping to prevent suspicion. But meanwhile, the virus can launch and carry out background tasks.

And hyperlinks are another major threat. Because people tend to trust PDFs, they likewise tend to trust any links embedded in the body of the file. Malicious actors can then use these links to lead you to harmful sites.

Most anti-malware software can identify and block the threats associated with PDF viruses. But they tend to be successful anyway because users are less likely to do their due diligence and check PDFs for potential dangers.

Practicing Strong PDF File Security

The biggest threat of a PDF virus is the fact that many users tend to trust PDFs over web pages and other potential threats. But the fact is that they can be used to deploy malicious software just as well as any other internet file.

Vigilance is the price of your security. To protect yourself from PDF file viruses, you must extend the same cybersecurity best practices to all files you might encounter.

Further, it’s important to remember that new threats emerge all the time. To protect yourself from malware and other threats, be sure to follow our latest cybersecurity guides.