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How to spot and avoid PDF malware

by Mic Johnson

There is a constant battle between internet users or companies and cybercriminals in the digital world. Each day, the latter develops sophisticated measures to breach the former’s security. As such, web users and corporate establishments have to stay updated with the latest cybersecurity threats. Before discussing digital vulnerabilities, we need to understand how they work.

To gain backdoor access to user information, hackers use various methods. One of the most common is getting malware (malicious software) into their victim’s device. This is usually attached to a file – image, audio, video or digital document. A PDF is a common file that introduces malware into your phone or computer.

Also known as Portable Document Format, this file works and supports links, images and written content. It can support both visible and non-visible types of data. PDFs’ flexibility and cross-platform nature make them a suitable carrier for delivering malicious codes. For those asking, “can PDF have viruses?” As explained above, the properties of PDFs allow them to do so.

The PDF can be used to steal your data or corrupt your device. In addition, the cybercriminal can also use these files to create a backdoor that will grant them unrestricted access to your private and financial information.

How to Spot PDF Malware

Now that we have established that PDF files are used to bypass security, let’s examine ways to spot them.

The PDF Has Hyperlinks

It is standard practice for PDF files to have hyperlinks. They can be used within the document to navigate different pages swiftly, especially if there are many pages. The headings or subheadings are linked to their corresponding pages on the document. Clicking on the link skips in-between pages and takes you to the page you are looking for.

Similarly, hyperlinks can be linked to external websites. Clicking on the anchor text redirects to the website. This is where things get tricky. This is because the hacker can insert links to malicious sites that can steal your data and alter your device. Sometimes, visiting these webpages results in automatic downloads of more malicious files.

The PDF Is Encoded

While hyperlinked PDF malware requires you to click on the link, some viruses infect your computer simply because you viewed them. These type of files are encoded with a malicious program that executes itself immediately after you open it.

For those who do not understand how it works, a virus is software like every other program on your computer. The difference is the type of command that they execute. They can alter certain functions on your device and cause it to malfunction. Most often than not, this type of PDF malware is often tricky to detect.

JavaScript Is Embedded into the PDF

JavaScript is a programming language. It can be used to create interactive elements that influence function and interface. While most web developers use it to create user-friendly webpages, hackers utilize it to introduce malware to your computer. The reason this is possible is that PDF can read JavaScript codes. If you open a JavaScript-embedded PDF, you will notice strange-looking texts alongside readable content.

PDFs with Multimedia Contents

As mentioned earlier, audio and visual content can be formatted into PDFs. Hackers know this and typically use it to transmit malware to your computer. They attack the malicious code to elements of this multimedia content. Playing or viewing them will cause the virus to alter your computer’s functions.

How to Avoid PDF Malware

Users can always protect themselves despite the different vulnerabilities associated with downloading or viewing a PDF. One way to avoid this type of malware is using a secure PDF reader like Adobe Acrobat. In addition, you can also view the PDF directly in your web browser without downloading it.

In addition, ensure to install comprehensive antivirus software on your computer. Norton, Clario, Avast, Kaspersky, and many others provide complete security. After installing these cybersecurity programs on your computer, set them up to automatically scan every PDF before enabling you to download it.

Here are other means to protect yourself:

  • Never click on unknown or unverified links. Instead, hover your cursor around the anchor text. This will reveal the URL of the website you will be redirected to.
  • Manually disable your PDF viewer from reading reading JavaScript texts.
  • Finally, never download PDF files from malicious websites. Only get these documents from trusted platforms.


While the threat of PDF malware is imminent, it can be prevented. Most time, hackers can gain access to your information when you do not do your due diligence. Taking the measures mentioned in this article can significantly reduce your chances of getting hacked via a malicious PDF.

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