eBook worms: PDF files that you download from free ebook websites can contain viruses. Let’s learn how to spot and avoid PDF malware. (2023)

Table of contents

  • How can a PDF file contain a virus?
  • Are PDF books safe?
  • How can an infected PDF contaminate your computer?
  • Malicious scripts in PDFs
  • Malware disguised as PDFs (PDF phishing)
  • Emails with infected PDFs
  • Fake clickbait books
  • Is it safe to download free PDFs from internet libraries and search engines?
  • Where to download ebooks without viruses?
  • How safe are other ebook formats?
  • What rules to follow to avoid getting a bookworm?

The Portable Document Format — or PDF as we know it — is probably one of the most frequently used file formats for sending documents. It can be found everywhere from schools to offices and banks, successfully replacing print-outs — and that's why malicious actors love it, too.

Can a PDF file contain a virus? The answer is definitely yes, but it's not the text or illustrations in PDFs that can harm your device. Instead, it's everything else in these files combined with the reader software that activates possible threats.

PDF files are not easily editable compared to rich text files like Microsoft Word's DOCX or Apple's PAGES files. Since you cannot just open a PDF and edit it as you please (even if you have special and often pricey software), PDFs are used for contracts, bank statements, and any other important documents that need to be signed and sent.

The “fill & sign” abilities of PDFs are where the danger lies. They work inside PDFs with the help of special scripts. Unfortunately, this means that malicious code can be lurking within or alongside such scripts. And a virus hiding within a PDF file can quickly infect your computer, be it a PC or even a Mac.

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When you download a book, hard-to-find scientific report, or free PDF template for your small business (especially if such documents come from untrustworthy websites), you might find a nasty surprise inside. Worse still — your PDF might turn out to be nothing but a virus disguised as a PDF file.

Let's see what dangers can hide within PDF files and how to counter them.

How can a PDF file contain a virus?

PDFs can have viruses that come embedded with a code that makes documents signable and (somewhat) editable. The mechanics are very similar to virus-infected Microsoft Word files. While their malware hides inside macros scripts, an infected PDF file will contain malicious JavaScript code.

Are PDF books safe?

A PDF is not an executable file, so it cannot infect your machine while sitting idle on your hard drive — the malware in a PDF needs to be interpreted and executed through PDF reader software.

This is why a PDF virus cannot infect most older e-readers and modern e-paper and e-ink books. Dedicated e-reader devices run an extremely abridged version of Linux OS or a custom OS under the hood, so are unable to interpret and run malicious scripts.

Unfortunately, Android-based e-readers with regular touchscreens (devices like Amazon's Kindle Fire) are potentially vulnerable. iOS devices should be safe from viruses in PDF files due to app memory sandboxing. However, many viruses are emerging for iOS, too, so it's worth being cautious.

PC and Mac machines are the most vulnerable to threats hidden in ebooks. This is because the software for opening and editing PDF files on desktop and laptop computers can interpret and run the malicious code injected by a hacker.

How can an infected PDF contaminate your computer?

Let's look at how PDF files containing malware infect your computer and where such files usually come from.

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Malicious scripts in PDFs

PDFs often contain scripts for extended capabilities. For example — in addition to fill and sign functionality — they can display the current date, add print buttons, format data, perform calculations on the input, etc. It's possible to add such scripts with the help of JavaScript using software like Adobe Acrobat Pro. Unfortunately, hackers will likely use more technically intricate ways to add malicious code to PDF files.

PDF files need PDF reading software to open and display their contents. This way, PDF readers become unwilling accomplices of hackers because either the apps themselves or their plugins will be able to run the injected code. Third-party plugins in PDF-reading software can also be a gateway for malicious scripts — if possible, you should disable them.

eBook worms: PDF files that you download from free ebook websites can contain viruses. Let’s learn how to spot and avoid PDF malware. (1)

Malware disguised as PDFs (PDF phishing)

You have probably heard about email phishing — hackers send you emails pretending to be somebody else and try to make you click links that will either steal your data or infect your computer with a virus. There are two PDF-related variations of phishing:

Emails with infected PDFs

An approach very similar to regular phishing. As a rule, such emails are executed better than generic phishing emails and target specific recipients. The content of the email won't have suspicious links. Still, it will contain either PDF files with viruses in the scripts, download links to malware files, or have a trojan virus disguised as a PDF in the attachment (something like document.pdf.exe).

Fake clickbait books

These PDF files pretend to be the books you want to download online. While looking for a specific book or document online, you might come across a free download link.

Initially, it might look like you've struck gold — the author, title, and cover match what you were looking for. Then, there is a proper intro, maybe even a couple of pages the hackers took from an official preview available online.

However, a few pages in, the text ends, and there is a download link that supposedly leads you to a complete copy of this book. Best case — the link will take you to a paid site with pirated content. Worst case — the link will download a virus. So don't risk it, and avoid clicking such links.

Is it safe to download free PDFs from internet libraries and search engines?

The initial question that should be asked about online libraries — isn’t downloading free pdf books illegal? It's not illegal to download books that are either free or have entered the public domain due to copyright expiration. However, most books on such websites like PDFdrive are pirated content. Their disclaimers usually warn against downloading any books you have no right to download for free.

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PDFdrive is one of the largest collections of free PDF downloads. So is PDFdrive safe? It contains everything from legitimately free books, educational materials, and voluntarily shared files, to pirate content — the danger is that anybody could add ebook files with any malware lurking inside at some point.

While websites like PDFdrive, Library Genesis, or Internet Archive try to keep their sites and content safe — most of that content is stolen, isn't checked for copyright infringements, and can be hijacked and added there by anyone including cybercriminals.

Trojan fake PDF files and malicious scripts can sneak into any PDF that you try to download. IPirate sites do try to provide their readers with quality content to keep them returning to watch or click the ads. However, it's impossible to keep track of billions of books, documents, magazines, etc.

eBook worms: PDF files that you download from free ebook websites can contain viruses. Let’s learn how to spot and avoid PDF malware. (2)

Apps that offer free ebook downloads carry all the same dangers as free online libraries. Often, they are nothing but an app-based wrapper or a shortcut to some external online library. What's worse — such installable apps can be gateways to malware for your iPhone, iPad, or Android phone.

eBook worms: PDF files that you download from free ebook websites can contain viruses. Let’s learn how to spot and avoid PDF malware. (3)

So, it looks like free online libraries are not just tempting sources of freebies, but decent malware repositories, too. Luckily, there are places where you can download books legally and sometimes even for free.

Where to download ebooks without viruses?

The safest places for buying and downloading ebooks are reputable booksellers like Amazon, Barnes & Noble, the book sections on iTunes or GooglePlay, official online book stores, or direct downloads from the living authors. They also feature public domain books for free so you don’t have to splurge immediately to have something interesting to read.

Ultimately, the safest way to obtain and read ebooks is to do it via an official distributor. Especially so when your target device is a dedicated e-paper or e-ink device reader and not a fully-functional smart tablet in disguise (Kindle Fire, we're looking at you). This way, you also won't have to worry about the format of the book you're about to download.

How safe are other ebook formats?

Are ebook formats other than PDF as likely to contain viruses? Well, it's much harder, but still possible to sneak a virus into a MOBI or AZW file for Kindle. An infected EPUB (preferred ebook format for iPhones and iPads) can also be a real thing because EPUB files are essentially special archive files containing HTML, CSS, and JavaScript scripts.

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But as said before, malicious code needs interpreters. So digital e-ink/e-paper e-readers are most likely to be safe even with an infected ebook on board. However, if such files are opened on your computer, there might be consequences.

What rules to follow to avoid getting a bookworm?

As you've learned, even seemingly harmless PDF or EPUB files can infect your computer. So if you really need a book, but it cannot be bought through a reliable online vendor, before you download from some shady website, try to:

  • Look for it at the library. You'd be amazed at the finds at your local library or the library of your local college or university.
  • Find out if you can buy it directly from the author or the current copyright holders.
  • Look for a different format — the book could be available as an audiobook or a video lecture.

If all of this fails and you must get a book from a free online library, there are ways to keep your devices safe.

How to avoid getting a virus from a PDF (or another ebook format):

  1. Use a pre-moderated online library requiring registration (like Scribd).
  2. Make sure there are no mistakes in the book title or the author's name. If there are, then you might have spotted a fake.
  3. Don't open the ebook directly on your computer — use cloud readers (for example, PocketBook Cloud or Google Drive's preview capabilities) instead of opening suspicious files on your machine.
  4. If you must open the book on your computer, disable third-party party plugins and JavaScript execution in your e-reader's settings.
  5. Scan the PDF file for a virus with antivirus software before opening it.
  6. Don't click any links inside the book or document.

If you suspect that a PDF file has already infected your computer, run a full antimalware check using your antivirus software.

The only bulletproof way to keep your device protected from malware in books and other media files is by running regular scans for viruses. Having real-time anti-malware protection on both your mobile and desktop devices is essential too. With Clario, you will get all of this plus a team of security professionals ready to help at the touch of your fingertips. Start your free 7-day trial with Clario now.

Use these precautions, and don't download suspicious PDF files from non-trustworthy websites if you can avoid it. It's better to pay for a book than for repairs to your machine if it gets infected. Happy reading!

Read more:

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FAQs

Can you get a virus from downloading a PDF? ›

Yes, they can. Because PDFs are one of the most universally used file types, hackers and bad actors can find ways to use these normally harmless files — just like dot-com files, JPGs, Gmail, and Bitcoin — to create security threats via malicious code.

Can you get a virus by downloading an ebook? ›

Unless it's from a trusted retailer, some ebooks may contain malicious software that can install malware, spyware, and viruses in your computer. Do not distribute ebooks unless the company or author allows it.

How do I know if my PDF has a virus? ›

How to Check PDF Virus? If you ever receive any PDF from any untrusted sources, it is recommended to scan the file before opening it. Email providers like Gmail have inbuilt malware scanner for file attachments. They implement the technology of VirusTotal so you can be assured.

Is it safe to download PDF books? ›

Are PDF books safe? A PDF is not an executable file, so it cannot infect your machine while sitting idle on your hard drive — the malware in a PDF needs to be interpreted and executed through PDF reader software. This is why a PDF virus cannot infect most older e-readers and modern e-paper and e-ink books.

Can you get a virus on your phone from opening a PDF? ›

These PDF files look like a regular document but that's not the truth. It looks locked out and blurred to misguide and make the user curious to open it. These kinds of malicious documents are designed to lure the user into opening such documents. This is a key entry point for the malware to the device.

Can an iPhone be hacked by a PDF? ›

Unless your phone was jailbroken, simply downloading a pdf will not cause any problems. Keep the iPhone updated to the latest iOS always and never Jailbreak. That's it.

Are free ebooks safe? ›

Yes, but only if you download them from reputable websites or the store on your device. We at Norton appreciate the importance of books and the value they add to your lives.

How do you know if a download is a virus or not? ›

You can use free software called VirusTotal to check for malware on links – before you even click them- as well as files you have already downloaded.
  • Go to: www.virustotal.com.
  • Select whether you want to check a link or file you have downloaded.
30 Sept 2021

What do I do if I think I downloaded a virus? ›

If your PC has a virus, following these ten simple steps will help you to get rid of it:
  1. Step 1: Download and install a virus scanner. ...
  2. Step 2: Disconnect from internet. ...
  3. Step 3: Reboot your computer into safe mode. ...
  4. Step 4: Delete any temporary files. ...
  5. Step 5: Run a virus scan. ...
  6. Step 6: Delete or quarantine the virus.

How can you tell if a PDF is real? ›

To do so, open the document in Adobe Acrobat or Adobe Reader. Click the Signature Panel icon then click “Validate All” then “OK”. The software will run a validation check to see if the digital certificate used to sign the document is valid.

How do I remove a virus from a PDF? ›

Scan PDF for virus
  1. From the menu bar, go to Tools, and then select Preferences.
  2. Find the preferences for JavaScript, and click on them.
  3. Remove the tick from the checkbox next to Enable JavaScript Actions.
17 Sept 2019

Can iPhones get viruses? ›

Can iPhones get viruses? Though rare, iPhones can get viruses and other malware, especially if the phone is jailbroken or if the victim is targeted in a high-value spear phishing attack. For normal iPhone users, a malware infection is an unlikely event.

Can hackers watch my iPhone? ›

Can an iPhone be hacked remotely? An iPhone can be hacked remotely through iOS vulnerabilities. However, it's more likely that it'll be hacked through malicious software or physical access, as programming-based hacking is the most difficult to carry out.

Can a hacker see me through my iPhone? ›

On top of that, popular app developers aren't immune to accusations of watching you through your phone's camera. Generally, however, a stalker would need to install spyware on your device in order to compromise it. Hackers can gain access to your phone physically, through apps, media files, and even emojis.

Can I scan my iPhone for hackers? ›

There's no definite way to check for every type of hack. Experts told us that one reliable way to investigate is to download a mobile security app called iVerify, which scans your phone's operating system for suspicious behavior and can also detect if your phone has been jailbroken.

Is downloading free ebooks legal? ›

Each eBook's detail page lists helpful information about it (e.g. author name, genre, word count), and once you've found the eBook of your choice, you can download it in popular formats like EPUB, MOBI, and PDF. Nearly all of the eBooks are public-domain, and are fully legal to download.

Is it illegal to download ebooks for free? ›

It isn't legal to upload or download copyrighted material without permission, but that isn't stopping students from doing it.

How do you tell if you got a virus? ›

If it's a viral illness, typically symptoms are shorter lasting and classically the symptoms include fever, chills, sore throat, nasal congestion, runny nose, cough, and a lot of times you can have some body aches. A lot of times the symptoms last for maybe three days to a week and then slowly get better over time.

Are virus Warning real? ›

Is the Google virus warning real? No. When Google says you have a virus on your phone, you are being scammed. Specifically, cybercriminals are trying to trick you into installing malware, submitting personal data, or paying for virus removal.

Can something download without you knowing? ›

Websites you visit can download and install software without your knowledge or approval. This is called a drive-by download. The objective is usually to install malware, which may: Record what you type and what sites you visit.

Does wiping a computer remove viruses? ›

In most cases, a factory reset will remove viruses. But how exactly do some manage to survive it? Wherever your backup data is stored, make sure you scan it for malware before moving any of it back to your device. The recovery partition is part of the hard drive where your device's factory settings are stored.

Can you get a virus by opening a file? ›

Most users get viruses from opening and running unknown email attachments. Never open anything that is attached to an email message unless you know the contents of the file.

How can I tell if my PDF is being tracked? ›

Adobe PDF usually has a pop-up warning to tell users if they are being tracked.

How can you tell if a PDF is unprotected? ›

Using your computer's basic Adobe Reader software, you can determine the security settings of any PDF file.
  1. Double-click on the PDF file that you want to open. Adobe Reader or Acrobat should open automatically. ...
  2. Click on the “File” menu.
  3. Click “Properties.” A new window opens on screen.
  4. Click the “Security” tab.

How can you tell if a PDF is secure? ›

To view the security settings of a document, choose File > Properties in Acrobat or Reader. From the Document Properties dialog box, click the Security tab. If you have trouble opening a PDF, or you're restricted from using certain features, contact the author of the PDF.

Is it safe to open a PDF in an email? ›

Yes, PDFs can be harmful. History has already shown us that the combination of an email and a malicious PDF attachment can be quite devastating, with losses reaching millions of dollars. That's why it's important for organizations to think about email protection.

How do I safely download an ebook? ›

Here are some general rules to apply when downloading e-books.
  1. Only use legitimate, trusted, well known retailers.
  2. If a book costs money on most other websites, the publisher is unlikely to have consented to its being offered for free somewhere else. ...
  3. Never download an ebook you know to be pirated.

Can you get viruses on Kindle? ›

This operating system is no more than a fork of Android, meaning that the code and the structure of the system are basically the same. Since any Android device can catch malware, it's possible for Kindle Fire to get it too.

Can a Kindle book have a virus? ›

Can a computer virus attach itself to an ebook? Most Amazon Kindle eBooks are DRM-protected files and computer viruses won't be able to infect these ebook files.

When you download an eBook where does it go? ›

Android phones and tablets

This will download the book directly to your Google Play Books app. Your download may begin without notification, so please check the app for your book a few minutes after you click the download button.

Where can I download books safely? ›

5 Best Sites to Download Free PDF Books in 2022
  • Open Library.
  • Bookboon.
  • PDF Books World.
  • Project Gutenberg.
  • ManyBooks.
13 Jan 2022

Do Kindles get hacked? ›

Once the malicious e-book is opened, hackers can get access to the Kindle and carry out activities like deleting your entire library and steal information like your Amazon credentials. Hackers could even turn your Kindle into a malicious bot and then gain access to other devices connected to your Wi-Fi.

How do u know if your tablet has a virus? ›

The signs that your phone has been infected with a virus or malicious malware include:
  • Your phone is operating slower.
  • Apps are taking longer to load.
  • The battery drains faster than expected.
  • You're experiencing a lot of pop-up ads.
  • Your phone has apps you don't remember downloading.
  • Unexplained increase in data usage.

Do I need antivirus for Kindle? ›

Installing protection software on your Kindle device is entirely optional. Your device is not inherently insecure without one installed, but can be installed if you prefer the extra layer of security that protection software apps can provide. Available options can be found on the Amazon App store.

Can a virus infect a tablet? ›

Malware can infect mobile devices in a variety of ways such as through an app, phishing email, or SMS text message. Think about all the personal information you access across all of your devices. It's available through your email, social media, financial accounts, and all the apps you use.

Can a Kindle be tracked? ›

Turn On Manage Your Device

Swipe down from the top of the screen to open Quick Settings, and then tap Settings > Device / Device Options > Find My Kindle / Find Your Tablet.

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