How to remove ARJ malware (Virus Removal Guide)

ARJ malware is the name for malware associated and spread by .ARJ files. The .ARJ file format was originally introduced in the late 1980s as a compression method for storing and sharing files more efficiently. Developed by Robert K. Jung, it was widely used before more modern formats like ZIP and RAR became dominant.

While .ARJ files themselves are not inherently malicious, cybercriminals have weaponized them to distribute malware. Because they are less commonly used today, many security programs do not scan them as rigorously as other archive formats, making them an attractive tool for attackers. These files are often used in phishing emails and malicious downloads, where victims unknowingly extract malware from an .ARJ archive that appears to contain legitimate content.

Once extracted, the malware can execute harmful scripts, install trojans, ransomware, spyware, or keyloggers, and even provide remote access to attackers. Most victims are tricked into opening these files through business email compromise (BEC) scams, fake invoices, or disguised software downloads.

What is an .ARJ file?

An ARJ file is a compressed archive format developed in 1989 by Robert K. Jung. It was designed to store multiple files within a single archive, reducing their size for easier storage and transfer. Similar to ZIP and RAR formats, ARJ was widely used in the early days of computing, particularly on DOS-based systems, for software distribution, backups, and file sharing. It became popular because of its high compression efficiency, especially for text-based files, and its ability to create multi-volume archives, allowing large files to be split across multiple floppy disks.

Despite its initial popularity, ARJ files eventually became obsolete due to the rise of more advanced compression formats like ZIP, RAR, and 7z, which offered better speed, compatibility, and encryption options. Today, very few modern programs support ARJ files, and most users rarely encounter them unless dealing with legacy software or old archived data. However, cybercriminals have revived the ARJ format for malware distribution because many modern security tools do not prioritize scanning ARJ archives, making them a useful tool for bypassing antivirus detection.

An ARJ file typically has the “.arj” file extension and requires specialized software, such as ARJ.EXE (the original utility), WinRAR, or 7-Zip, to extract its contents. Unlike ZIP and RAR, ARJ does not have widespread native support on modern operating systems, meaning users must install third-party tools to open these archives. This lack of mainstream use has contributed to its exploitation by hackers, who use ARJ files to hide malware within compressed archives and distribute them through phishing emails, fake software downloads, and malicious websites.

Key Features of ARJ Files

1. High Compression Efficiency: Originally provided better compression for text-based files than early ZIP formats.
2. Multi-Volume Support: Allowed large files to be split across multiple floppy disks.
3. DOS-Based Origin: Primarily used on early MS-DOS and Windows systems.
4. Obsolete Format: Replaced by ZIP, RAR, and 7z due to better performance and security.
5. Requires Third-Party Software: Not natively supported on modern systems.
6. Exploited by Hackers: Used for hiding malware because modern security tools rarely scan them.

Because ARJ files are now rarely used in legitimate applications, receiving an unsolicited ARJ file—especially from an unknown email or website—is a strong indicator of a malware attempt. Users should never open an ARJ file from an untrusted source and should always scan archives with antivirus software before extracting their contents.

Are .ARJ files safe?

ARJ files are not inherently dangerous. They are simply compressed archive files, similar to ZIP and RAR, used to store multiple files in a single package. If an ARJ file comes from a trusted source and contains legitimate files, it is generally safe to open. However, since ARJ is an outdated format, most modern users rarely encounter it unless dealing with legacy software, old backups, or archives from the early days of computing.

That said, ARJ files can become dangerous when cybercriminals use them to conceal and distribute malware. Attackers take advantage of the fact that many modern security tools do not automatically scan ARJ archives, making them a useful method for bypassing antivirus detection. If an ARJ file contains malicious scripts, trojans, ransomware, spyware, or keyloggers, extracting and opening the contents can lead to system infection, data theft, or remote access attacks.

When Are ARJ Files Unsafe?

ARJ files are unsafe in the following situations:

1. Received from an Unknown Email or Sender
   • If an unsolicited ARJ file arrives in your inbox as an attachment, especially from an unknown sender, it is likely a phishing attempt.
   • Cybercriminals often disguise malicious ARJ archives as invoices, contracts, or order confirmations.
2. Downloaded from Untrusted Websites
   • If an ARJ file is obtained from torrent sites, cracked software repositories, or suspicious download pages, it may contain hidden malware.
   • Attackers frequently disguise ARJ archives as game cheats, software updates, or premium content to lure victims into downloading them.
3. Triggered by a Fake Alert or Pop-Up
   • Some compromised websites automatically trigger downloads of infected ARJ files, tricking users into opening them with fake security warnings or software update prompts.
   • If a site forces an ARJ file download, it is best to delete it immediately.
4. Contains Suspicious Executable Files
   • If extracting an ARJ archive reveals files with extensions like .exe, .bat, .vbs, or .scr, this is a major red flag.
   • Malicious ARJ archives often contain hidden trojans or keyloggers disguised as documents or application files.
5. Not Recognized by the Sender
   • If a colleague, supplier, or friend sends an ARJ file but claims they never sent it, their email may have been compromised.
   • Hackers use email spoofing to send infected ARJ attachments under familiar names.

Is an .ARJ file malware?

ARJ files themselves are not malware. They are compressed archive files, similar to ZIP or RAR, used to store multiple files in a single package. If an ARJ file comes from a legitimate source and contains safe files, it poses no security risk. However, because ARJ is an older and less commonly used format, it is often exploited by cybercriminals to distribute malware while avoiding detection by modern security software.

An ARJ file becomes malware when it is used to conceal and distribute malicious files. Hackers pack trojans, ransomware, keyloggers, or other malware inside an ARJ archive and trick victims into extracting it through phishing emails, fake software downloads, or malicious websites. Once the archive is opened and its contents are executed, the malware is installed on the victim’s system, leading to data theft, system compromise, or further infection.

To determine if an ARJ file is malware, users should consider where it came from and what it contains. If an ARJ file was unexpectedly received via email, downloaded from an untrusted website, or prompted by a suspicious pop-up, it should be treated as a potential threat. Always scan ARJ files with antivirus software before extracting them, and never open one unless you are certain of its legitimacy.

How is ARJ malware spread?

ARJ malware is primarily spread through phishing emails, where attackers disguise malicious ARJ files as invoices, contracts, or shipping confirmations. These emails often appear to come from trusted sources, such as banks, suppliers, or company executives, and urge recipients to download and extract the archive. Once opened, the malware inside the ARJ file executes, installing trojans, ransomware, or spyware that can steal sensitive information or give attackers remote access to the system.

Another common method is fake software downloads and malicious websites. Hackers disguise ARJ files as cracked software, game cheats, or security updates and distribute them through torrent sites, illegal streaming platforms, and phishing sites. Users who download and extract these archives unknowingly install malware onto their system. Some compromised websites also trigger automatic ARJ downloads, tricking users into opening them with fake security alerts or system update messages.

ARJ malware can also spread through business email compromise (BEC) and social engineering scams. Cybercriminals pose as executives or vendors and send malicious ARJ attachments disguised as financial reports, payroll files, or internal documents. Employees who believe these files are work-related may extract and execute the malware, leading to corporate data breaches, financial fraud, or widespread infections.

Common Ways ARJ Malware is Spread:

• Phishing Emails: Fake invoices or documents sent as ARJ attachments.
• Fake Software Downloads: Malware disguised as software, game cheats, or updates.
• Compromised Websites: Hacked sites that automatically download ARJ malware.
• Business Email Compromise (BEC): Hackers impersonate executives or vendors.
• Social Engineering Scams: Fake job offers, legal notices, or security updates.

To avoid ARJ malware infections, users should never open unsolicited email attachments, verify the sender before downloading files, and use antivirus software to scan all downloaded archives.

How to Remove ARJ Malware – Removal Guide

Follow these instructions to remove ARJ malware from your system. If you have downloaded or extracted an ARJ file from an untrusted source, your device may be infected with trojans, ransomware, spyware, or other malicious programs. To ensure complete removal, it is recommended to use a trusted malware removal tool and follow the manual steps carefully.

The guide below provides both automatic removal using Malwarebytes and manual removal instructions for users who prefer to delete threats manually. If you are unsure about the extent of the infection, start with an automatic scan, then proceed with manual steps if necessary.

How to Remove Using Malwarebytes

The easiest and most effective way to remove ARJ malware is by using Malwarebytes, a trusted security tool that detects and removes malware, including trojans, ransomware, spyware, and other threats hidden in ARJ archives. Follow these updated 2025 instructions to ensure complete removal.

Step 1: Download and Install Malwarebytes

1. Go to the official Malwarebytes website: Download Malwarebytes
2. Click Download Now and save the installer to your computer.
3. Open the downloaded file (MBSetup.exe) and follow the on-screen instructions to install Malwarebytes.
4. Once installed, launch Malwarebytes to begin the scanning process.

Step 2: Run a Full System Scan

1. Open Malwarebytes and go to the Dashboard.
2. Click Scan to start a full system scan.
3. Malwarebytes will analyze your system for ARJ malware, trojans, ransomware, and other threats.
4. Wait for the scan to complete. This may take a few minutes depending on your system.

Step 3: Remove Detected Threats

1. Once the scan is finished, Malwarebytes will display a list of detected threats.
2. Click Quarantine to move all detected malware to the quarantine folder.
3. If prompted, restart your computer to complete the removal process.

Step 4: Run a Second Scan for Confirmation

1. After rebooting, open Malwarebytes again.
2. Click Scan to run a secondary scan and verify that no traces of ARJ malware remain.
3. If Malwarebytes detects additional threats, quarantine and remove them.

Step 5: Enable Real-Time Protection (Optional but Recommended)

1. Go to Settings > Security in Malwarebytes.
2. Enable Real-Time Protection to prevent future infections.
3. Consider upgrading to Malwarebytes Premium for automatic protection against malicious downloads, phishing emails, and malware-packed ARJ files.

Final Step: Delete Suspicious ARJ Files Manually

Even after removing malware, leftover ARJ files may still be on your system. Manually delete any suspicious ARJ files from your Downloads, Temp, and AppData folders to prevent accidental execution.

Malwarebytes is one of the most effective tools for removing ARJ malware, and using it regularly will help keep your system safe. If you continue experiencing issues, repeat the scan or use an additional security tool for deeper detection.

How to Manually Remove ARJ Malware

Manual removal requires identifying and deleting malicious files, stopping suspicious processes, and cleaning system settings to prevent the malware from running again.

Step 1: End Malicious Processes

1. Open Task Manager by pressing Ctrl + Shift + Esc.
2. Go to the Processes tab and look for any suspicious processes that you do not recognize.
3. Right-click on the process and select End Task to stop it.

Step 2: Uninstall Suspicious Programs

1. Open Control Panel and go to Programs > Uninstall a Program.
2. Look for recently installed programs that seem suspicious or that you do not remember installing.
3. Click on the program and select Uninstall to remove it.

Step 3: Delete Malicious Files and Folders

1. Press Windows + R, type %AppData%, and hit Enter.
2. Look for unusual folders or files, especially those linked to the ARJ file you extracted.
3. Delete any suspicious files.
4. Repeat this process in the following locations:
   • %LocalAppData%
   • %ProgramData%
   • C:\Users[Your Username]\Downloads
   • C:\Users[Your Username]\AppData\Roaming
   • C:\Windows\Temp

Step 4: Remove ARJ Malware from Startup

1. Open Task Manager (Ctrl + Shift + Esc) and go to the Startup tab.
2. Look for unknown or suspicious startup programs and disable them.

Step 5: Clean Your Browser Settings

1. Open your browser and go to Extensions or Add-ons.
2. Remove any suspicious extensions that you did not install.
3. Clear cache and cookies to remove any stored malware traces.

Step 6: Reset Your Hosts File

1. Press Windows + R, type notepad C:\Windows\System32\drivers\etc\hosts, and press Enter.
2. If you see unknown or suspicious entries, delete them and save the file.

Step 7: Scan Your System with an Antivirus

Even after manual removal, some traces of ARJ malware may remain. Run a full system scan with a trusted antivirus or Malwarebytes to detect and remove hidden threats.

If the malware persists after following these steps, consider using an antivirus for a more thorough cleanup.