Can a PDF Have a Virus & How Can I Read PDF Files Safely?

As she excitedly clicked to open the PDF, her computer started behaving strangely. Unknown to her, the virus embedded within the file had started compromising her system's security. It began by collecting her personal information and tracking her online activities. As time went on, she started experiencing various issues with her computer. Her files became corrupted, her internet connectivity suffered, and, worst of all, her sensitive information was exposed.

Marquisha sought help from an IT professional who diagnosed her computer with a virus. The consequences of opening that seemingly harmless PDF were more severe than she could have imagined. Her personal and financial information was at risk, and it took considerable effort and time to clean her system and protect her digital identity.

To help you avoid the repercussions Marquisha faced by unknowingly clicking on a PDF infected with a virus, this article will explain the potential security risks associated with PDF files and how to read PDFs safely.

Overview of PDF Files and Their Popularity

pdf fileIt is well-established that malware can be embedded in various types of files, including PDFs. Cybercriminals continuously evolve their tactics, and PDFs remain a common means for spreading malware due to their widespread use and ease of exploitation.

PDF stands for Portable Document Format. It is an easily accessible tool that allows individuals to present and exchange documents no matter what software, hardware, or operating systems are being used at the time.

A PDF can contain links and buttons, form fields, audio, video, and business logic. This is considered the best way to present content in a format and method that's easy to follow. PDFs offer many advantages for users. For example, they can preserve formatting and layout across devices and operating systems. In addition, they are smaller, and it makes it easier for them to store, transfer, and download files. They also provide advanced security features like encryption and password protection, safeguarding sensitive business information.

PDFs offer businesses and individuals a reliable and professional document format that guarantees consistency, security, and accessibility. Furthermore, there are more advantages to why millions love the PDF and what it provides. One specifically is security. 

PDFs are highly secure and can be password protected, encrypted, and certified for digital signatures. This makes them ideal for sensitive documents such as contracts, legal documents, and financial statements.

PDFs offer several security options to protect sensitive information. One of the most common methods is encrypting the PDF and securing it with a password. By encrypting the PDF, unauthorized individuals cannot copy or access the information contained within the file. To further enhance security, you can set different types of passwords for editing and opening the PDF file. It is important to choose a strong password to ensure the highest level of security.

In addition to passwords, adding a digital signature to a PDF file can enhance its security. While a digital signature does not prevent changes from being made to the PDF, it serves as proof that the document has not been modified after the signature was added. This verification helps ensure the integrity and authenticity of the PDF file. Digital signatures can be created using PDF converter tools like PDFCreator, and they help to verify the identity of the sender and protect against tampering or unauthorized modifications.

Another aspect of PDF security is setting permissions for different users or groups. PDFs allow you to restrict certain actions, such as printing, copying, or editing the content. By controlling these permissions, you can ensure that only authorized individuals can perform specific actions on the PDF file. This feature is particularly useful when sharing sensitive documents with a limited audience, as it provides an extra layer of protection against unauthorized use or distribution of the file. Implementing these security measures can help safeguard confidential information and ensure the integrity of PDF files.

How Can You Stay Safe from PDF Threats? Are Viruses Lurking in Your Files?

download pdf button laptop screen downloading document concept file with pdf label down arrow signAlthough PDFs have many advantages and are trusted by millions, it is important to know that even PDFs can have viruses. The popularity of PDFs makes them a favorite target among malware attackers. 

PDFs can carry embedded malware or viruses, exploiting vulnerabilities in software to infect the user's device. For instance, an infected PDF file could contain a seemingly harmless image. However, when the user opens the file, it triggers a hidden script that downloads malware onto their computer. A malicious PDF can initiate a file download to your local computer. Cyber attackers often trick users into opening PDF files that contain malicious code. Once the PDF file is opened, the embedded code can exploit security vulnerabilities in PDF readers like Adobe Reader or Acrobat, potentially resulting in the download and execution of malware or other malicious files. It is important to exercise caution when opening PDF files from unknown or untrusted sources to minimize the risk of downloading malicious content.

Opening a PDF file with malicious malware does not necessarily require you to click on and run the malicious file that was just downloaded. Simply opening the PDF file itself can potentially infect your computer with malware.

PDF files can contain embedded malicious code that can exploit vulnerabilities in PDF readers, such as Adobe Reader and Acrobat. This code can be designed to automatically execute and infect your computer when the PDF file is opened.

It's important to note that the risk of infection depends on the specific vulnerabilities present in the PDF reader software you are using. Keeping your PDF reader and other software updated with the latest security patches can help mitigate the risk of exploitation.

Therefore, your computer can be infected by opening a PDF file with malware, even without clicking on additional content or running any files within the PDF itself.

As stated, PDFs are one of the best ways to get and send files easily. But it’s important to remember that as easy as it is to navigate PDFs, it is also easy for viruses, malicious links, and much more to take advantage of PDF users.

Can a PDF Have a Virus?

PDF files usually have images, interactive forms, hyperlinks, and multimedia content to make them more understandable. This makes it easy for hackers to hide viruses in these forms. 

Javascript

PDFs can incorporate JavaScript code within the document, which offers a range of functionalities and enhances the overall user experience. However, cybercriminals can also exploit this feature to spread viruses and malicious content. By embedding harmful JavaScript code within the PDF, attackers can create an environment where opening the PDF triggers the execution of this malicious script. The script can then automatically download and install a virus or malicious software on the user's computer without their knowledge or consent. This vulnerability poses considerable risks to the user, including exposing their sensitive data, enabling unauthorized access to their system, or inflicting damage to their device and software. As a result, users must exercise caution when opening PDF files, ensuring they originate from reputable sources, and keep their PDF reader software updated with the latest security patches to mitigate such risks.

Multimedia Content

PDFs can contain multimedia content such as images, videos, or sound files, increasing their usefulness and interactive capacity. However, this multimedia content can also pose a risk as it can be a vehicle for delivering viruses. Malicious software can be embedded into this multimedia content, and when the PDF file is opened, it triggers the execution of this harmful code. For instance, a PDF may contain an image that seems safe, but behind the scenes, a hidden script within the image is activated once the PDF is opened, causing malware to be downloaded and executed on the user's device. Therefore, this potential for malware delivery makes it crucial for users to exercise caution and only open PDF files from trusted sources.

Hyperlinks 

PDF files can also contain clickable links, adding another layer of usefulness and interactivity to the document. However, this feature can be exploited by threat actors as a means to distribute malicious content. These malicious links, when clicked, could redirect a user to a dangerous website designed to steal sensitive information (phishing) or automatically download and install harmful software on their device. The risks posed by these links are significant, ranging from unauthorized access and data breach to system damage and disruption. Given these threats, users must scrutinize the links in PDF files before clicking, especially if the file came from an unknown or untrusted source.

Learning how to defend against PDF viruses is very important for users to fight against hacking. Some examples include:

  1. Recognizing phishing attempts: If you receive an email that seems suspicious, especially if it claims to be from a reputable organization like a financial institution, it's important not to interact with it. Instead, directly contact the organization through their official channels to verify the email's authenticity. This way, you can protect yourself by avoiding any engagement with potentially harmful emails. Using authentication methods for trusted collaborators and only open files from reliable sources is also beneficial. Adobe Acrobat Sign offers identity authentication features to enhance security.
  2. Using a trusted PDF reader: To defend against PDF viruses, utilizing reputable software and ensuring it is regularly updated is crucial. While several PDF viewers are available, not all of them actively update their security measures to combat malicious activities. Adobe Acrobat Reader, the industry standard for viewing and working with PDFs, frequently releases security updates that help protect users.
  3. Running regular virus scans: Most operating systems, such as Windows and macOS, have built-in antivirus software. While third-party cybersecurity programs are often unnecessary, it is still advisable to regularly scan your system using the antivirus scanner embedded in your operating system. This helps ensure any potential threats are detected and addressed.

Common Types of PDF Viruses 

cyber virus Viruses in PDFs can be of several types:

  • PDF Trojans: steal information from your machine and send it to the attacker. This way, unwanted third parties can access your personal or banking information, company data, photos, documents, etc. An example of a PDF Trojan is Lurk Trojan, which can hijack a user's device and steal sensitive information such as banking credentials, usernames, and passwords. This Trojan can be distributed via malicious PDF files that, once opened, install malware onto the user's device, giving the attacker access to private information stored on the device.
  • PDF Malware: is focused on destroying information on your device or changing it. This can mean injecting ads into your browser or encrypting information on your device to demand ransom (that’s ransomware). An example of PDF malware is the Locky ransomware, which is distributed via spam campaigns and can be delivered through a PDF attachment that, once opened, enters the victim's system and encrypts files, demanding payment for their release.
  • Droppers: Due to the limitations to the payload a PDF can bring onto your device, a lot of PDF viruses are actually just droppers, i.e., a way to get the target user to download the main malicious file. This can be done in various ways, from executing code to get your browser to open the right page to something as innocuous as simply linking to a malicious website in an otherwise normal ebook or scientific paper. An example of a dropper is the Bladabindi malware, which is a RAT (Remote Access Trojan) distributed through PDF files containing malicious macros. Once enabled by the user, these macros download and execute the malware, giving an attacker remote access to the victim's device.

In summary, PDF Trojans steal information, PDF malware destroys, or changes information and droppers are used to deliver other types of malware to the user's device.

What Are the Risks of Opening a Malicious PDF File?

When it comes to PDF files, cybercriminals can take the elements of that PDF and embed harmful code or even multiple links, which can compromise user’s devices and sensitive data. 

Embedding links in PDF files and users and businesses making the mistake of clicking on them can lead to dangerous websites or downloads of malicious content that can harm millions who don’t know what’s on the other side. 

Several different types of malware attacks use PDFs as a delivery method. Many include high-profile attacks. Here are some examples:

  • Agent Tesla: has been active since 2014. It is often delivered as a malicious attachment in phishing emails. In addition, it can steal data from mail clients, web browsers, and File Transfer Protocol (FTP) servers. This malware can also capture screenshots, videos, and Windows clipboard data. It can also lead to credentials and tokens being available on the Dark Web for use by criminal actors. Agent Tesla is available online for purchase under the guise of being a legitimate tool for managing your personal computer. Its developers continue to add new functionality, including obfuscation capabilities and targeting additional applications for credential stealing.

  • AZORult: It has been in business since 2016. It is usually delivered through phishing, infected websites, exploit kits (automated toolkits exploiting known software vulnerabilities), or dropper malware that downloads and installs AZORult. This can be used to steal information from compromised systems. It has been sold on underground hacker forums for stealing browser data, user credentials, and cryptocurrency information. AZORult’s developers are constantly updating their capabilities.

  • FormBook: malware that has been active since 2016 and is usually delivered as an attachment in phishing emails. It is an information stealer advertised in hacking forums. FormBook is capable of keylogging and capturing browser or email client passwords.

How Can I Read PDF Files Safely?

When downloading PDF files and determining whether they’re safe, users have to think about where the source of the file is coming from. For example, is it through the website or an email attachment? If you trust the source, your next step is checking that the file is actually in PDF format and not just a ruse to get you to download an executable malware file. In most cases, a PDF virus will need you to open the file in a reader to execute its malicious code.

Following simple steps ensures readers' safety when opening PDF files. First, make sure you have reliable antivirus software installed on your device. Antivirus software can detect and block malicious files, including infected PDFs. Keep your software and operating system current to benefit from the latest security patches and bug fixes.

Furthermore, be cautious when downloading and opening PDF files from unknown or suspicious sources, including emails. Stick to reputable websites and sources, and verify the file's legitimacy before opening it. If you receive a PDF via email or an unknown sender, exercise even more caution and consider scanning it with your antivirus software before opening it.

Also, ensure you use a reputable PDF reader from a certified source, which enables you to put more trust in protecting your security by acting as a guard against potential threats.

Lastly, remember that staying informed is key. Keep yourself updated about the latest cybersecurity threats and best practices. By being aware of the risks and taking appropriate precautions, you can minimize the chances of falling victim to a malicious PDF.

Our Final Thoughts on Safely Navigating PDF Files

Opening a PDF can be risky if you simply trust the file without knowing if malicious links or security risks are waiting on the other side. Both businesses and users must know when it is safe to open a PDF file and how to do so securely without having their personal data taken.

Many PDF exploits require users to open the file in a specific reader or use an add-on extension for a malicious script to work. Users must remember only to download those PDFs to their devices that they are sure come from reliable sources, turn off the automatic download of email attachments in their mail client, and scan their system regularly to ensure their device is malware-free.

The simplest protection method is to keep your software updated and use robust passwords to protect sensitive information. A secure, private, trusted Internet connection can also go a long way in keeping you and your data protected.

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