The answer to the “Can PDFs have viruses in them?” question is yes, which means they can compromise your security, privacy, data, and devices. The risk is especially high considering the popularity of the PDF format—its compatibility across platforms and ease of sharing make it a common target.
With that in mind, it’s important that you know how to check if a PDF has a virus and learn how malicious PDF files can harm your system.
In this article, we’ll explore PDF security risks, focusing on how to tell secure PDFs from those carrying malware. In addition, we’ll offer a few helpful tips on protecting your PDFs against viruses. Let’s begin!
How Hackers Exploit PDFs and Use Them to Deliver Viruses
Hackers exploit PDFs and use them to deliver viruses in several ways, including embedding malicious scripts or macros, exploiting software vulnerabilities, hiding malware in attachments and links, and enabling dangerous content through social engineering.
Let’s explore these more closely to understand how PDFs can carry viruses:
#1. Embedding Malicious Scripts or Macros
PDFs can have viruses in the form of malicious scripts or macros that turn them into dangerous tools. These small programs start running automatically as soon as you open the file. They can cause a number of issues, such as installing malware on your computer, stealing your data, or even giving hackers remote control of your system.
The worst part about a PDF file carrying these viruses is that it looks completely normal. For this reason, you should only open PDFs from trusted sources.
#2. Exploiting Software Vulnerabilities in PDF Readers
Hackers commonly target PDF reader vulnerabilities, also known as bugs. They look for these weaknesses and craft malicious PDFs to exploit them. For example, when hackers identify a bug, they might write code that triggers it when you open the file.
Simply put, PDFs can have viruses that activate as soon as you open the document. This allows hackers to manipulate your files and create backdoors for future attacks.
#3. Hiding Malware in Attachments or Links
Hackers often hide malware in PDFs in attachments and links that look like harmless documents or images. However, if you click on them, you can get redirected to a dangerous website or download malicious content onto your computer. This is one of the major ways PDFs can have viruses like ransomware and spyware.
It’s noteworthy that hackers often disguise these PDFs as invoices, resumes, or other common files to trick you into opening them.
#4. Using Social Engineering to Enable Dangerous Content
PDFs can have viruses that specifically target your personal information. Hackers often use social engineering to design the malicious file to look like something most people would be interested in, like a job offer.
This misleads users into opening a link or allowing permissions, unintentionally activating the virus hidden in the file and giving hackers access to their sensitive data.
That said, this method relies on human error rather than a bug. In fact, a hacker can tailor their message based on your interests or contacts to make the infected PDF file appear trustworthy. This version of social engineering is known as spear phishing.
3 Key Signs that Your PDF Might Be Malicious
Now that we know the answer to the question, “Can PDFs have viruses?” let’s look into some key signs your PDF might be malicious. These include unusual file size or content behavior, requests for suspicious permissions, and unexpected pop-ups.
#1. Unusual File Size or Content Behavior
The simplest way to check if a PDF contains a virus is to look at its size. Namely, a simple document like a resume or invoice shouldn’t be hundreds of megabytes. If it is, it’s likely malicious—hackers tend to hide malware in large files to make it harder to detect.
Another red flag is the file’s unusual behavior—if it takes too long to open or keeps crashing your reader, it may be infected.
#2. Requests for Suspicious Permissions
If you try to open a PDF file and see a request asking you to install a piece of software or grant some other suspicious permission, you’re probably being targeted by hackers. Following their instructions can open doors for them to exploit your personal information and manipulate your data from afar.
#3. Unexpected Pop-Ups
Getting unexpected pop-ups when you download a PDF file can be a sign of scareware. This is a type of virus designed to trick you into believing your system is infected and prompt you to visit a dangerous website or install an antivirus program that’s actually malware. Needless to say, if you comply, you’ll allow hackers access to your system and data.
What Happens if You Open a PDF Containing a Virus?
If you open a PDF containing a virus, you’re potentially exposed to various security risks. “Potentially” is the operative word here—merely opening a malicious file doesn’t automatically mean your device will get infected.
In other words, a virus may be coded to attack your system only if you click on a specific image or link where it’s hidden.
Conversely, some malicious PDF files release malware into your device as soon as you view them.
That said, the consequences of interacting with an infected file (or its elements) depend on the hacker’s intention. Some aim to infect your device with spyware to collect your personal information and commit identity theft or fraud. Others have financial motives and use ransomware to get you to pay them to regain control of your device.
Whatever the hacker’s intention, if you open a suspicious PDF on your phone or computer, back up your data immediately and run trusted antivirus software to scan your device.
4 Tips on How to Protect Your PDFs Against Viruses
To protect your PDFs against viruses, you should use a trusted PDF tool, avoid downloading files from random sources, regularly update software, and disable JavaScript in PDF readers.
Let’s look into these methods in more detail:
#1. Use a Trusted PDF Tool
Using a trusted PDF tool is the best way to keep your private information and devices safe when printing PDF files. One such tool is the pdf.net editor, which allows you to convert other file formats into PDF and vice versa and edit your files while preventing unauthorized access.
It’s important that the PDF tool you choose regularly updates its software. This can minimize security vulnerabilities and stop hackers from installing viruses and stealing your data.
#2. Avoid Downloading PDFs From Untrusted Sources
When downloading PDFs, make sure they’re coming from reliable sources. More often than not, hackers will try to infect your system by sending you an unsolicited email with a PDF attachment. If you see a sender you don’t recognize, especially in your spam folder, it’s best not to open their message at all.
That said, you should be wary of a suspicious email, even if it’s sent from someone you know. As previously mentioned, hackers can customize their messages based on your contacts to mislead you into downloading a malicious file.
#3. Update Software Regularly to Fix Security Vulnerabilities
Updating software regularly can reduce the number of security vulnerabilities, which are essentially cracks in the system through which hackers slip viruses. Namely, your PDF reader and browser may have limited security measures, and your antivirus scanner may fail to detect malware before you open an infected file.
In this scenario, your operating system may need to protect itself, which is why it’s essential that you keep all your software up to date.
#4. Disable JavaScript in PDF Readers
Hackers tend to hide malware in JavaScript code within a PDF file, so you should disable JavaScript plug-ins in your PDF reader. This is especially important when you’re opening PDF files from unknown sources—this way, if the document is malicious, it won’t execute destructive JavaScript code.
How to Scan a PDF for Viruses
You should always scan a PDF for viruses, especially if you don’t know its source. You can do it on your computer or use an online virus scanner—here’s how:
Scanning a PDF file on Windows:
- Open the Windows Security app.
- Select Custom scan to check a specific file.
- Click Scan now and choose the PDF file you want to scan.
Scanning a PDF file on Mac:
- Open the CleanMyMac app.
- Select the Protection option from the sidebar.
- Tap on Scan.
Scanning a PDF file with an online virus scanner:
- Upload the PDF document into an online scanner.
- Start the scanning process.
- Review the results.
Protect your important files and personal information with PDF.net.
- We use advanced safety protocols and HTTPS encryption to protect your documents from intruders.
- As soon as you finish using our services, your uploads will be automatically deleted to ensure maximum privacy.
- Personal data on our servers is regulated by the General Data Protection Regulation (GDPR).