Can Viruses Come From a PDF?

Yes, viruses can come from a PDF by hiding in malicious code. A virus is a type of malware, which is malicious software intended to infect your device and steal private data. A virus can infect your device only if you interact with it, which could happen by opening a PDF containing a virus. Since PDFs are so widely used, hackers can hide viruses within innocent-looking files to jeopardize your privacy.

Continue reading to learn how PDFs can contain viruses, what happens when you open a virus-infected PDF and how you can stay protected against malicious PDFs.

How PDFs can contain viruses

Viruses can hide inside a PDF in a variety of ways, mainly through code, system commands and embedded objects. Most web browsers support JavaScript, a programming language, and its code can be found in PDFs. When a hacker wants to use a PDF with malicious intent, they can hide a virus’s code within JavaScript to take advantage of any security vulnerabilities within a PDF. A virus can start infecting other files and applications on your device by simply opening a malicious PDF file. Hackers may assume that you have antivirus software installed to find, stop and eliminate any known viruses, so they may embed hidden objects in PDF files to go undetected.

What happens if you open a PDF containing a virus?

Every virus is created differently, and in some cases, merely opening a PDF containing a virus may not trigger malware to infect your device. However, some viruses are coded to immediately harm your device with malware just by viewing the infected PDF file. A hacker may code a virus to infect your device only if you’ve interacted with a specific element of the PDF file where the virus resides. For example, you may receive a PDF file in an unsolicited email, but malware may not impact your device unless you click on a specific link or image within the PDF.

What happens when you open a PDF containing a virus will depend on what a hacker wants with your information. Some hackers may want to infect your device with spyware, which will monitor your online activity and collect your private information for a hacker to commit fraud or identity theft. Other hackers may be motivated by financial gain and can infect your device with ransomware, which will stop you from using your device until you’ve paid a ransom. Regardless of a hacker’s motive, when you interact with a virus within a PDF, it will do whatever the hacker has programmed it to do. A hacker can cause a virus to steal your private information, give them unauthorized access to your device or even spread additional malware to other systems.

How to stay protected against malicious PDF files

You can keep your private information safe from malicious PDF files by avoiding interaction with suspicious emails, checking for viruses and keeping your software up to date.

Never interact with suspicious emails

Suspicious emails are likely to contain a link or attachment, like a PDF file, that contains a virus. You should never interact with any suspicious emails because they could be phishing emails sent by hackers impersonating people you trust to trick you into sharing your private information. You can tell if an email is a phishing attempt if it is sent from an unfamiliar email address, uses urgent or threatening language, contains spelling or grammatical errors or has suspicious links or attachments. A hacker will assume that you might click on a PDF file out of curiosity in a phishing email, and by doing so, you could trigger a virus infection on your device. Most email service providers will display a warning on any email they consider suspicious, so it’s important to pay attention to these warnings and know the signs of phishing emails.

Check PDFs for viruses before opening them

Most antivirus software can detect, prevent and remove known viruses from infecting your device, so you should use antivirus software to scan any PDFs for viruses before opening them. After you install antivirus software, you can use it to scan a single PDF you suspect contains a virus or your entire device at once. Whichever antivirus software you choose, once it’s downloaded to your device, launch the software and start a scan of a specific PDF file or your entire device. Antivirus software will compare your device’s contents to a large database of known viruses and malware, and if it finds a match, the software will automatically isolate the virus and remove it before it can infect your device.

Use secure PDF readers

You should use a secure PDF reader to keep your private information safe from hackers who could gain unauthorized access through viruses. A PDF reader is software that allows you to view, edit and print PDF files while offering ways to restrict other people’s controls to prevent unauthorized access. Although many PDF readers exist, you should choose a secure one that frequently updates its software to defend against security vulnerabilities. Since viruses hidden in PDF files could exploit your device’s security flaws, it’s important to use a trustworthy PDF reader that will stop hackers from installing malware or stealing your data. When using a PDF reader, you should disable JavaScript plugins, since JavaScript code is a common place for hackers to hide viruses within PDFs.

Keep your software and Operating System (OS) up to date

An easy way to protect yourself against viruses hidden in PDFs is to keep your software updated. The latest software updates typically patch security vulnerabilities, add new features, fix bugs and improve your device’s overall performance. When you install the latest version of your device’s Operating System (OS), you’re protecting yourself from cyber threats, such as virus infections.

Mark phishing emails as spam

If you’ve received a suspicious email with a PDF attachment and think it is a phishing attempt, you should mark the email as spam and report it immediately. Marking phishing emails as spam helps your email service provider better identify emails that may contain viruses or suspicious content in the future. For example, if you receive an email that you know is spam and simply delete it, the same sender can continue sending phishing emails, and your email service provider will not understand that you’ve faced a cyber threat. By marking phishing emails as spam, you keep the malicious sender out of your inbox and teach your email service provider what to look out for when filtering emails.

Avoid falling victim to malicious PDF attachments

You may receive many suspicious emails and know not to interact with them, but don’t let a PDF attachment fool you into clicking on something that could infect your device with a virus. Although not all PDF files containing viruses will infect your device just by viewing them, you should always be cautious by avoiding interaction with suspicious links or attachments, checking PDFs for viruses with antivirus software and marking phishing attempts as spam.