UNITED STATES—Portable Document Files (PDFs) are likely to be an essential part of your personal and professional life. It’s hard to imagine that opening them could do any harm. The problem is that they may contain malicious code that will infect your system. PDF files can do much more than display text. This, together with the fact that so many people use them, makes them a popular delivery method for cybercriminals. They will use techniques such as creating deceptive hyperlinks or embedding malicious JavaScript in PDFs.

Can just opening a PDF put your computer at risk? 

In most cases, you have to click a link or perform some other action before a virus activates in an infected PDF. But there is an exception. You can trigger an infection when you open a PDF if your PDF reader is vulnerable. Attackers can exploit a weakness in the PDF reader to embed malicious code.

Signs that a PDF could contain malware

You can spot certain warning signs that a PDF could contain malware. Popular signs include receiving a PDF from an unknown sender or receiving a PDF with a file extension that looks odd. A legitimate PDF will come from someone you know and have a proper file name rather than a generic or vague file name. If you receive an email message that urges you to open a PDF immediately, this is another big red flag. A legitimate PDF shouldn’t ask you to provide private data. To overcome these common yet dangerous threats, using the Moonlock cybersecurity engine is what many people do. Since the tool is perfectly customized for common users, it’s popular among all age groups, including students, working professionals, etc.

Essential steps to prevent PDF virus attacks

A few best practices can significantly lower the risk of infection and help you maintain open PDF security.

  • Make sure you use a trustworthy PDF reader and keep it up to date.
  • You need to use tools that offer real-time scanning for malware on your device. They will inspect files as you open or download them to offer immediate protection against malware threats. The tool may quarantine a file to prevent it from harming your system.
  • A cloud viewer or sandbox allows you to open a PDF in a safe environment so you don’t expose your main system to potential threats.
  • Don’t download PDFs or open PDF attachments from unknown senders or obscure sites. Always try to verify the source first and the best way to do this is to contact the sender using a different method to ask if they really sent it. 
  • Don’t just click on links in a PDF. They could take you straight to a website that looks legitimate and ask for your personal details.
  • Unless you have a good reason to keep JavaScript on in your PDF reader, you should turn it off. You may not use it, but cybercriminals often use it for attacks. 
  • If you’re a Mac user, think about uninstalling Adobe Acrobat and using the Preview app in Finder instead.

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Digital parenting – teach safe habits at home

PDF security is a household issue. Family members often download resources from the internet and children may go to untrustworthy sites to download games or music. If they don’t have guidance, they could put the whole home network at risk of infection from PDF malware. Parents must address cybersecurity with all household members to ensure this doesn’t happen.

  • Clearly explain the dangers of malware hiding in files like PDFs that seem harmless. Set device permissions so children can’t change critical settings or install software.
  • Give the family a set of rules to follow online. One of these rules could be that they should ask for your guidance if they want to download resources.
  • Show family members the types of red flags to look for that could mean a PDF contains malware. Awareness can prevent them from taking unnecessary risks. 
Photo courtesy of Ed Hardie.

What to do if you’ve opened a malicious PDF

You may be aware of the risks, but you can still mistakenly open a malicious PDF. Once this happens, you need to take action quickly to limit the damage. 

  • Disconnect from the internet straightaway. This stops the command server from communicating with the malware.
  • If you use the best antivirus programs, they will constantly scan to detect and remove malware before it does any damage. Run a full scan anyway to make sure.
  • Change your passwords straight away, starting with your bank password. You should also change your email and social media passwords.
  • You may need to consider wiping and resetting your device and in this case, you will need backups of all your files. This may seem like overkill, but you could potentially lose all your data if you open a PDF that contains malware.
  • You should place a fraud alert on your credit report if you believe you’re a victim of fraud or you suspect your identity has been stolen.

Wrapping up

Opening a PDF isn’t always dangerous but you shouldn’t just open them without a second thought. Cybercriminals like to use them as tools to embed malicious code or phishing links. Awareness of the signs of PDF malware can help to stop you from falling victim to hidden threats. Even family members in your household need to be aware of the dangers or your home network could be infected. The above tips should help you to prevent yourself from putting your computer at risk.