Remove the .pdf ransomware infection

Also Known As: .pdf virus
Distribution: Low
Damage level: Severe

.pdf ransomware removal instructions

What is .pdf ransomware?

.pdf is a ransomware-type infection that belongs to the Dharma ransomware family. As with most of infections from this family, .pdf was discovered by Jakub Kroustek. After successful infiltration, .pdf encrypts most stored data, thereby rendering it unusable. Additionally, it renames each file by appending the victim's ID, developer's email address, and ".pdf" extension. For example, "sample.jpg" might be renamed to a filename such as "[].pdf". Note that the ".pdf" is extension is a genuine Portable Document Format (PDF) and, therefore, encrypted files are likely to have a PDF file icon. Despite this, do not be tricked - files are certainly encrypted, not just their formats changed. Once encryption is complete, .pdf opens a pop-up window (HTML application) and stores the "RETURN FILES.txt" text file on the desktop. Updated variants of this ransomware use the ".[].pdf" extension for encrypted files.

The new text file delivers a short message stating data is encrypted and encourages victims to contact .pdf's developers. The HTML application provides much more information. It states that files are compromised using RSA-1024 cryptography and that a unique decryption key is necessary to restore them. Unfortunately, this information is accurate. RSA-1024 is an asymmetric algorithm designed to generate two unique keys for each victim. The public key is used to encrypt data, whilst the private key is used to decrypt it. Victims cannot access their private keys - these are stored on a remote server controlled by .pdf's developers. Therefore, these people are able to blackmail victims by offering paid recovery of files. The cost of decryption is currently unknown, however, size of ransom usually fluctuates between $500-$1500, and criminals demand payment in a cryptocurrency such as Bitcoins, Moneros, DASH, Ethereum, or other. Note that .pdf developers offer free decryption of one file (up to 1 MB, non-archived) to 'prove' that they are capable of restoring data and to gain the victim's trust. Do not pay, even if you can afford to. Ransomware developers often ignore victims, once payments are submitted. Therefore, paying is likely to deliver no positive result and you will be scammed. Ignore all requests to submit payments or even contact these people. There are no tools capable of cracking RSA-1024 encryption and restoring data free of charge. Therefore, you can only restore everything from a backup, if one has been created.

Screenshot of a message encouraging users to pay a ransom to decrypt their compromised data:

.pdf decrypt instructions

.pdf is virtually identical to dozens of other ransomware-type infections such as Sguard, Cetori, and NEMTY PROJECT. Although the developers are different, all ransomware infections are virtually identical. Most compromise data (usually, by encryption) so that developers can make ransom demands by offering paid recovery of files. Encryption is performed using AES, RSA, and other similar cryptographies that generate unique decryption keys. Therefore, unless the virus is not fully developed or has bugs/flaws, restoring data manually (without developers' involvement) is impossible. Ransomware infections are one of the main reasons why you should maintain regular backups, however, store them on a remote server (e.g., Cloud) or unplugged storage device (external hard drive, Flash drive, or similar), since locally stored backups are compromised together with regular data. In fact, have multiple backup copies stored in different locations, since there is always a chance that servers/storage devices can be damaged.

How did ransomware infect my computer?

The way developers proliferate .pdf is currently unconfirmed, however, these infections are usually distributed using trojans, fake software updaters and 'cracks', spam emails, and third party download sources (e.g., Peer-to-Peer [P2P] networks, freeware download websites, free file hosting sites, and similar). Trojans are lightweight malicious applications that stealthily infiltrate computers and inject them with additional malware. Fake updaters and cracks infect systems rather than updating/activating software. Spam email campaigns are used to send hundreds of thousands of deceptive emails containing malicious attachments (e.g., links/files) and messages that describe these attachments as various 'important documents' (e.g., receipts, invoices, bills, etc.) and encourage recipients to open them. The same applies to unofficial download sources, which criminals use to present malicious executables as genuine software, often tricking users into manual download/installation of malware. In summary, careless behavior and lack of knowledge of these threats are the main reasons for computer infections.

Threat Summary:
Name .pdf virus
Threat Type Ransomware, Crypto Virus, Files locker
Encrypted Files Extension .pdf (this ransomware also appends filenames with the victim's unique ID and developer's email address)
Ransom Demanding Message RETURN FILES.txt text file, pop-up window (HTML application)
Cyber Criminal Contact
Detection Names Avast (Win32:RansomX-gen [Ransom]), BitDefender (Trojan.Ransom.Crysis.E), ESET-NOD32 (A Variant Of Win32/Filecoder.Crysis.P), Kaspersky (, Full List Of Detections (VirusTotal)
Symptoms Cannot open files stored on your computer, previously functional files now have a different extension (for example, my.docx.locked). A ransom demand message is displayed on your desktop. Cyber criminals demand payment of a ransom (usually in bitcoins) to unlock your files.
Distribution methods Infected email attachments (macros), torrent websites, malicious ads.
Damage All files are encrypted and cannot be opened without paying a ransom. Additional password-stealing trojans and malware infections can be installed together with a ransomware infection.
Malware Removal (Windows)

To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Malwarebytes.
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How to protect yourself from ransomware infections?

The key to computer safety is caution. Therefore, pay close attention during the download/installation/update processes, and when browsing the Internet in general. Download your programs from official sources only, preferably using direct download links. Proper software maintenance is paramount. Keep installed applications up-to-date, however, software updates should be performed using implemented functions or tools provided by the official developer only. Use of third party downloaders/installers/updaters is risky, since these tools often include rogue applications. Note that software piracy is a cyber crime and many cracking tools are fake - using them is risky. Therefore, never attempt to activate installed applications using third party/illegal tools. Handle all received email attachments with care. Files/links that are irrelevant and those received from suspicious/unrecognizable email addresses should never be opened. Have a reputable Internet security suite installed and running - this will detect and eliminate malware before the system is harmed. If your computer is already infected with .pdf, we recommend running a scan with Malwarebytes for Windows to automatically eliminate this ransomware.

Text presented in .pdf ransomware pop-up window (HTML application):

You can send us up to 1 file for free decryption. The total size of files must be less than 1Mb (non archived), and files should not contain valuable information. (databases,backups, large excel sheets, etc.)
When you make sure of decryption possibility transfer the money to our bitcoin wallet. As soon as we receive the money we will send you:
1. Decryption program.
2. Detailed instruction for decryption.
3. And individual keys for decrypting your files.
Do not rename encrypted files.
Do not try to decrypt your data using third party software, it may cause permanent data loss.
Decryption of your files with the help of third parties may cause increased price (they add their fee to our) or you can become a victim of a scam.

Screenshot of .pdf text file ("RETURN FILES.txt"):

.pdf text file

Text presented within this file:

All your data is encrypted!
for return write to mail:

Screenshot of files encrypted by .pdf (".pdf" extension):

Files encrypted by .pdf

.pdf ransomware removal:

Instant automatic malware removal: Manual threat removal might be a lengthy and complicated process that requires advanced computer skills. Malwarebytes is a professional automatic malware removal tool that is recommended to get rid of malware. Download it by clicking the button below:
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Quick menu:

Step 1

Windows XP and Windows 7 users: Start your computer in Safe Mode. Click Start, click Shut Down, click Restart, click OK. During your computer start process, press the F8 key on your keyboard multiple times until you see the Windows Advanced Option menu, and then select Safe Mode with Networking from the list.

Safe Mode with Networking

Video showing how to start Windows 7 in "Safe Mode with Networking":

Windows 8 users: Start Windows 8 is Safe Mode with Networking - Go to Windows 8 Start Screen, type Advanced, in the search results select Settings. Click Advanced startup options, in the opened "General PC Settings" window, select Advanced startup. Click the "Restart now" button. Your computer will now restart into the "Advanced Startup options menu". Click the "Troubleshoot" button, and then click the "Advanced options" button. In the advanced option screen, click "Startup settings". Click the "Restart" button. Your PC will restart into the Startup Settings screen. Press F5 to boot in Safe Mode with Networking.

Windows 8 Safe Mode with networking

Video showing how to start Windows 8 in "Safe Mode with Networking":

Windows 10 users: Click the Windows logo and select the Power icon. In the opened menu click "Restart" while holding "Shift" button on your keyboard. In the "choose an option" window click on the "Troubleshoot", next select "Advanced options". In the advanced options menu select "Startup Settings" and click on the "Restart" button. In the following window you should click the "F5" button on your keyboard. This will restart your operating system in safe mode with networking.

windows 10 safe mode with networking

Video showing how to start Windows 10 in "Safe Mode with Networking":

Step 2

Log in to the account infected with the .pdf virus. Start your Internet browser and download a legitimate anti-spyware program. Update the anti-spyware software and start a full system scan. Remove all entries detected.

If you cannot start your computer in Safe Mode with Networking, try performing a System Restore.

Video showing how to remove ransomware virus using "Safe Mode with Command Prompt" and "System Restore":

1. During your computer start process, press the F8 key on your keyboard multiple times until the Windows Advanced Options menu appears, and then select Safe Mode with Command Prompt from the list and press ENTER.

Boot your computer in Safe Mode with Command Prompt

2. When Command Prompt mode loads, enter the following line: cd restore and press ENTER.

system restore using command prompt type cd restore

3. Next, type this line: rstrui.exe and press ENTER.

system restore using command prompt rstrui.exe

4. In the opened window, click "Next".

restore system files and settings

5. Select one of the available Restore Points and click "Next" (this will restore your computer system to an earlier time and date, prior to the .pdf ransomware virus infiltrating your PC).

select a restore point

6. In the opened window, click "Yes".

run system restore

7. After restoring your computer to a previous date, download and scan your PC with recommended malware removal software to eliminate any remaining .pdf ransomware files.

To restore individual files encrypted by this ransomware, try using Windows Previous Versions feature. This method is only effective if the System Restore function was enabled on an infected operating system. Note that some variants of .pdf are known to remove Shadow Volume Copies of the files, so this method may not work on all computers.

To restore a file, right-click over it, go into Properties, and select the Previous Versions tab. If the relevant file has a Restore Point, select it and click the "Restore" button.

Restoring files encrypted by CryptoDefense

If you cannot start your computer in Safe Mode with Networking (or with Command Prompt), boot your computer using a rescue disk. Some variants of ransomware disable Safe Mode making its removal complicated. For this step, you require access to another computer.

To regain control of the files encrypted by .pdf, you can also try using a program called Shadow Explorer. More information on how to use this program is available here.

shadow explorer screenshot

To protect your computer from file encryption ransomware such as this, use reputable antivirus and anti-spyware programs. As an extra protection method, you can use programs called HitmanPro.Alert and EasySync CryptoMonitor, which artificially implant group policy objects into the registry to block rogue programs such as .pdf ransomware.

Note that Windows 10 Fall Creators Update includes a "Controlled Folder Access" feature that blocks ransomware attempts to encrypt your files. By default, this feature automatically protects files stored in the Documents, Pictures, Videos, Music, Favorites as well as Desktop folders.

Controll Folder Access

Windows 10 users should install this update to protect their data from ransomware attacks. Here is more information on how to get this update and add an additional protection layer from ransomware infections.

HitmanPro.Alert CryptoGuard - detects encryption of files and neutralises any attempts without need for user-intervention:

hitmanproalert ransomware prevention application

Malwarebytes Anti-Ransomware Beta uses advanced proactive technology that monitors ransomware activity and terminates it immediately - before reaching users' files:

malwarebytes anti-ransomware

  • The best way to avoid damage from ransomware infections is to maintain regular up-to-date backups. More information on online backup solutions and data recovery software Here.

Other tools known to remove .pdf ransomware:

About the author:

Tomas Meskauskas

Tomas Meskauskas - expert security researcher, professional malware analyst.

I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats. Contact Tomas Meskauskas.

PCrisk security portal is brought by a company RCS LT. Joined forces of security researchers help educate computer users about the latest online security threats. More information about the company RCS LT.

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Removal Instructions in other languages
Malware activity

Global malware activity level today:

Medium threat activity

Increased attack rate of infections detected within the last 24 hours.

QR Code
.pdf virus QR code
A QR code (Quick Response Code) is a machine-readable code which stores URLs and other information. This code can be read using a camera on a smartphone or a tablet. Scan this QR code to have an easy access removal guide of .pdf virus on your mobile device.
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