JS:Cryptonight virus (Removal Guide) - updated Aug 2019

JS:Cryptonight virus Removal Guide

What is JS:Cryptonight virus?

JS:Cryptonightminer is the name Avast and AVG vendors give malicious crypto-mining script embedded on various sites, although can also be a false-positive

JS:Cryptonight virus mines MoneroJS:Cryptonight is categorized as one of crypto-miners that illegally mines Monero on the infected system

JS:Cryptonight is a cryptominer that uses Cryptonight algorithm to mine Monero and is based on JavaScript.[1] The unique feature of malware is that it can affect both Windows and Mac operating systems. The trojan might enter the system via malicious spam emails or other stealthy methods and immediately start utilizing the GPU and CPU of the affected device for illegal cryptocurrency mining. The mined funds are immediately transferred to a preset crypto wallet, generating money regularly for the threat actors behind the JS:Cryptonight malware.

While the detection might mean that your browsers are infected, it can also be a false-positive,[2] as users reported that they were getting the JS: CryptoNightMiner-A [Trj] alert on legitimate sites like YouTube. In such a case, it is recommended updating Google Chrome, Mozilla Firefox, or another users browser along with AVG or Avast security software to stop false alarms.

If, however, the infection is present it is vital to get rid of JS:Cryptonight miner as soon as possible, as its malicious background processes might compromise the computer security and result in further malware infections, wear out the hardware, and also result in increased electricity bills. For that, please scan your computer with reputable anti-malware software as soon as possible.

Name JS:Cryptonight
Also known as JS: CryptoNightMiner-A [Trj], JS:CryptonightMiner-a
Type Trojan horse/cryptominer
Danger level Medium. Initiates system changes, misuses computer's CPU and GPU for crypto mining
Symptoms Sluggish computer performance, unknown processes running in the Task Manager
Distribution methods Bogus downloads, corrupted websites
Main dangers Computer hardware damage, other malware infection, infiltration of other malware
Elimination To get rid of this trojan virus, use FortectIntego

As we have mentioned, JS:Cryptonight virus might enter the system after downloading the malicious email attachment. However, it can also infect it after visiting a questionable website, for instance, illegal video streaming or web game site. If you have antivirus installed on your PC and it is up-to-date, it is supposed to warn you about such activity.

JS: CryptoNightMiner-A [Trj] might also get into the system pretending to be a legitimate program or its update. Hence, the miner might be installed after downloading freeware or shareware. In this case, the malicious program initiates system changes and immediately starts using computer’s resources to mine cryptocurrency.

JS:Cryptonight virusJS:Cryptonight is a term used by many antivirus programs to identify a cyber threat on the system.

The miner runs on a Javascript algorithm called Cryptonight.[3] It is specially designed to mine Monero cryptocurrency which gains more and more popularity[4]. You can suspect that it was installed on your Mac or Windows computer if you see suspicious processes running in the Task Manager/Activity Monitor and notice sluggish computer performance. Sometimes the mining is initiated while visiting specific websites. In this case, the process should stop once you close these sites and leave them.

In case you believe you are infected, you should not try to remove JS:Cryptonight manually. Malware might consist of numerous different files which have to be erased as well. Additionally, other malicious programs may have been installed on your device too.

JS:CryptonightJS:Cryptonight generates illegal profits for its developers from mining Monero digital currency.

For this reason, it’s recommended opting for automatic JS:Cryptonight removal which requires scanning the system with anti-malware tool, such as FortectIntego. At the moment, AVG is detecting this virus as JS:CryptonightMiner-a or JS: CryptoNightMiner-A [Trj]. This task should not be delayed because, as you might have already understood, the virus can lead your PC to the loss of valuable information and similar issues. Such cyber threats have unlimited abilities, so make sure you keep an eye on them.

The dangers of JS:Cryptonight

Even though it is hard to identify that your system is infected with JS:Cryptonight virus, users report about multiple issues which are caused by this cyber threat in the long-run. Usually, a computer becomes noticeably slower and fails to load specific applications on a daily basis.

JS:Cryptonight minerSystems infected with JS:Cryptonight virus might start to crash, freeze or make browsing experience unbearable.

It is because JS:Cryptonight miner exploits high amounts of computing power to mine Monero digital currency. In other terms, the system is forced to reallocate all its resources to cryptocurrency mining for long periods of time. As a result, it operates at high temperatures for excessive amounts of time and has little resources left for essential processes.

Likewise, if JS:Cryptonight sneaks into your system, there is a substantial risk that you will face the following problems:

  • Increased latency;
  • Some programs might not load;
  • System crash;
  • Never-ending freezes.

JS:Cryptonight infection exampleThere are numerous other infections similar to JS:Cryptonight miner.

Furthermore, these are not the only dangers of JS:Cryptonight attack. Keep in mind that all infections, including crypto-malware, make computer's system vulnerable to other dangerous viruses. Thus, the presence of this Monero miner might increase the risk of occurrence of other potentially malicious programs.

Infiltration of cryptocurrency miner

The trojan horse might enter the system using a couple of methods. However, each of them requires user’s participation. Typically, malware is advertised as useful program or software update. Hence, users might install it themselves.

Usually, such programs are available on unauthorized file-sharing websites, P2P networks, torrents and similar questionable sources. For this reason, users are advised to stay away from such places. If you need a particular program, you should rely on developer’s websites only.

JS:Cryptonight malwareJS:Cryptonight virus targets Windows and Mac computers to mine Monero illegally.

Additionally, experts from LosVirus.es[5] remind that it’s important to pay attention to software installation process too. If you decide to install freeware or shareware, you need to use Advanced/Custom settings and opt out all pre-selected optional programs. Usually, they have more negative features than are beneficial to the user.

Keep in mind that Quick/Recommended settings do reveal what is hiding in the software bundle. Hence, if you use them, you give indirect permission to install all third-party applications without even knowing it.

Delete JS:Cryptonight virus from the machine

To remove JS:Cryptonight trojan virus from Mac or Windows correctly, you have to use powerful security software, such as FortectIntego or Malwarebytes. It doesn’t matter whether malware infected Mac or Windows device, automatic removal is the only safe method to remove cryptocurrency miner.

Manual JS Cryptonight trojan removal might not be effective. The miner might come back and continue its activities once you reboot the computer. Additionally, you might accidentally terminate legitimate system files which may lead to irreparable damage to the system.

do it now!
Fortect Happiness
Intego Happiness
Compatible with Microsoft Windows Compatible with macOS
What to do if failed?
If you failed to fix virus damage using Fortect Intego, submit a question to our support team and provide as much details as possible.
Fortect Intego has a free limited scanner. Fortect Intego offers more through scan when you purchase its full version. When free scanner detects issues, you can fix them using free manual repairs or you can decide to purchase the full version in order to fix them automatically.
Alternative Software
Different software has a different purpose. If you didn’t succeed in fixing corrupted files with Fortect, try running SpyHunter 5.
Alternative Software
Different software has a different purpose. If you didn’t succeed in fixing corrupted files with Intego, try running Combo Cleaner.

Getting rid of JS:Cryptonight virus. Follow these steps

Manual removal using Safe Mode

If JS:Cryptonight is blocking access to security software, follow these steps and get rid of this virus with the help of Safe Mode with Networking:

Important! →
Manual removal guide might be too complicated for regular computer users. It requires advanced IT knowledge to be performed correctly (if vital system files are removed or damaged, it might result in full Windows compromise), and it also might take hours to complete. Therefore, we highly advise using the automatic method provided above instead.

Step 1. Access Safe Mode with Networking

Manual malware removal should be best performed in the Safe Mode environment. 

Windows 7 / Vista / XP
  1. Click Start > Shutdown > Restart > OK.
  2. When your computer becomes active, start pressing F8 button (if that does not work, try F2, F12, Del, etc. – it all depends on your motherboard model) multiple times until you see the Advanced Boot Options window.
  3. Select Safe Mode with Networking from the list. Windows 7/XP
Windows 10 / Windows 8
  1. Right-click on Start button and select Settings.
  2. Scroll down to pick Update & Security.
    Update and security
  3. On the left side of the window, pick Recovery.
  4. Now scroll down to find Advanced Startup section.
  5. Click Restart now.
  6. Select Troubleshoot. Choose an option
  7. Go to Advanced options. Advanced options
  8. Select Startup Settings. Startup settings
  9. Press Restart.
  10. Now press 5 or click 5) Enable Safe Mode with Networking. Enable safe mode

Step 2. Shut down suspicious processes

Windows Task Manager is a useful tool that shows all the processes running in the background. If malware is running a process, you need to shut it down:

  1. Press Ctrl + Shift + Esc on your keyboard to open Windows Task Manager.
  2. Click on More details.
    Open task manager
  3. Scroll down to Background processes section, and look for anything suspicious.
  4. Right-click and select Open file location.
    Open file location
  5. Go back to the process, right-click and pick End Task.
    End task
  6. Delete the contents of the malicious folder.

Step 3. Check program Startup

  1. Press Ctrl + Shift + Esc on your keyboard to open Windows Task Manager.
  2. Go to Startup tab.
  3. Right-click on the suspicious program and pick Disable.

Step 4. Delete virus files

Malware-related files can be found in various places within your computer. Here are instructions that could help you find them:

  1. Type in Disk Cleanup in Windows search and press Enter.
    Disk cleanup
  2. Select the drive you want to clean (C: is your main drive by default and is likely to be the one that has malicious files in).
  3. Scroll through the Files to delete list and select the following:

    Temporary Internet Files
    Recycle Bin
    Temporary files

  4. Pick Clean up system files.
    Delete temp files
  5. You can also look for other malicious files hidden in the following folders (type these entries in Windows Search and press Enter):


After you are finished, reboot the PC in normal mode.

Remove JS:Cryptonight using System Restore

This method might also help to get rid of this Trojan virus with the help of System Restore method:

  • Step 1: Reboot your computer to Safe Mode with Command Prompt
    Windows 7 / Vista / XP
    1. Click Start Shutdown Restart OK.
    2. When your computer becomes active, start pressing F8 multiple times until you see the Advanced Boot Options window.
    3. Select Command Prompt from the list Select 'Safe Mode with Command Prompt'

    Windows 10 / Windows 8
    1. Press the Power button at the Windows login screen. Now press and hold Shift, which is on your keyboard, and click Restart..
    2. Now select Troubleshoot Advanced options Startup Settings and finally press Restart.
    3. Once your computer becomes active, select Enable Safe Mode with Command Prompt in Startup Settings window. Select 'Enable Safe Mode with Command Prompt'
  • Step 2: Restore your system files and settings
    1. Once the Command Prompt window shows up, enter cd restore and click Enter. Enter 'cd restore' without quotes and press 'Enter'
    2. Now type rstrui.exe and press Enter again.. Enter 'rstrui.exe' without quotes and press 'Enter'
    3. When a new window shows up, click Next and select your restore point that is prior the infiltration of JS:Cryptonight. After doing that, click Next. When 'System Restore' window shows up, select 'Next' Select your restore point and click 'Next'
    4. Now click Yes to start system restore. Click 'Yes' and start system restore
    Once you restore your system to a previous date, download and scan your computer with FortectIntego and make sure that JS:Cryptonight removal is performed successfully.

Finally, you should always think about the protection of crypto-ransomwares. In order to protect your computer from JS:Cryptonight and other ransomwares, use a reputable anti-spyware, such as FortectIntego, SpyHunter 5Combo Cleaner or Malwarebytes

How to prevent from getting mac viruses

Protect your privacy – employ a VPN

There are several ways how to make your online time more private – you can access an incognito tab. However, there is no secret that even in this mode, you are tracked for advertising purposes. There is a way to add an extra layer of protection and create a completely anonymous web browsing practice with the help of Private Internet Access VPN. This software reroutes traffic through different servers, thus leaving your IP address and geolocation in disguise. Besides, it is based on a strict no-log policy, meaning that no data will be recorded, leaked, and available for both first and third parties. The combination of a secure web browser and Private Internet Access VPN will let you browse the Internet without a feeling of being spied or targeted by criminals. 

No backups? No problem. Use a data recovery tool

If you wonder how data loss can occur, you should not look any further for answers – human errors, malware attacks, hardware failures, power cuts, natural disasters, or even simple negligence. In some cases, lost files are extremely important, and many straight out panic when such an unfortunate course of events happen. Due to this, you should always ensure that you prepare proper data backups on a regular basis.

If you were caught by surprise and did not have any backups to restore your files from, not everything is lost. Data Recovery Pro is one of the leading file recovery solutions you can find on the market – it is likely to restore even lost emails or data located on an external device.

About the author
Lucia Danes
Lucia Danes - Virus researcher

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