What is HKU\S-1-5-21?

HKU\S-1-5-21 belongs to the nasty Trojan threat that attacks Windows PC users all around the world. Normally it is installed without your knowledge when using computer improperly. It is very tricky that escapes from any detections. The infected may perform poorly as long as it gets insides, such as slow PC performance, computer freezing, high CPU and annoying ads redirections. Besides, HKU\S-1-5-21 virus has changes on the compromised computer like homepage provider, firewall setting and registry utilities. With being an aggressive computer threat, HKU\S-1-5-21 shows cookies to track your online history and habit for illegal purposes. To thoroughly terminate HKU\S-1-5-21 virus, a manual method would be needed to analyze its random locations so that it can be permanently gone from your computer. Unfortunately you are one of the victims of HKU\S-1-5-21 malware, it is strongly advised to remove it as quickly as you can. According to the analysis of users’ complains, HKU\S-1-5-21 virus is capable of revealing users’ private information into social networking which would lead to unexpected hackers attack Besides, the virus can automatically act as a key logger that seriously makes the urgent situation. Now eliminate HKU\S-1-5-21 with the guide below:


Manually Remove HKU\S-1-5-21 from Windows OS

If you have computer security problems on Mac OS, please read this Mac Guide – How to Clean and Protect Your Mac?

(NOTE: Bookmark this page first because some steps may close your web browser or restart computer)

Please Take A Moment To Read This

If you believe that your computer has been infected with malware, you should consider using Wipersoft Anti-malware to search for HKU\S-1-5-21 and other infections. Wipersoft is a professional Anti-malware Tool designed to identity, block and remove malware for PC.

Download WiperSoft Anti-malware

Quick Menu

Step 1. Remove HKU\S-1-5-21 related plug-in, toolbar, add-on, extension from Chrome/Firefox/IE/Edge

Step 2. Uninstall HKU\S-1-5-21 related programs from your computer;

Step 3. Change system folder settings to show all hidden files;

Step 4. Find and delete HKU\S-1-5-21 related files in hidden folders;

Step 5. Find and remove HKU\S-1-5-21 related registry files ;

Step 6. Reset Microsoft Edge, Chrome, Firefox and IE to remove HKU\S-1-5-21 related hijacker;

Step 1.Remove HKU\S-1-5-21 related extension from Microsoft Edge/ Chrome/Firefox/IE

Note – If you cannot find or remove a malicious extension, please read next step.



On Chrome

  • Click the Chrome menu on the browser toolbar.
  • Click Tools.
  • Select Extensions.
  • Click the trash can icon to delete extensions that may be related with HKU\S-1-5-21.
  • A confirmation dialog appears, click Remove.

  • Click the menu button and choose Add-ons.
  • In the Add-ons Manager tab, select the Extensions panel.
  • Select add-ons that may be related with HKU\S-1-5-21 and click Remove button
  • Click Restart now if it pops up.

  • Open the IE, click the Tools button , and click Manage add-ons.
  • Click Toolbars and Extensions on left side of the window., and then select extensions that may be related with HKU\S-1-5-21;
  • If the add-on can be deleted, you’ll see the Remove option. Click Remove and then click Close. Otherwise click Disable button.


  • Click More (…) on the address bar and select Extensions


  • Select extensions that may be related with HKU\S-1-5-21 and click Uninstall button









Step 2.Uninstall HKU\S-1-5-21 related programs from your computer

1. Press Win + R keys at the same time to launch Run box >> Then input: “Control Panel” and click OK

uninstall HKU\S-1-5-21

HKU\S-1-5-21 uninstall

2. In Control Panel, click on Uninstall a program

HKU\S-1-5-21 uninstalling

3. In the Programs and Features window, right click on apps that may be related with HKU\S-1-5-21, then click Uninstall/Change. Then select Uninstall option.

Note – If you cannot find or remove malicious program, please continue the below steps.

Step 3.Change system folder settings to show all hidden files

Win 7 / Vista User

HKU\S-1-5-21 removal for win 7

  • Right-click the Windows Logo button and choose Open Windows Explorer.
  • Click Organize and choose Folder and Search Options.
  • Click the View tab, select Show hidden files and folders and then clear the checkbox for Hide protected system operating files.
  • Click Yes on the warning and then click OK.
Win 8 UserHKU\S-1-5-21 removal for win 8

  • On your keyboard press the Windows + E keys.
  • Click the View tab.
  • Check File name extensions and Hidden items

Win 10 User

HKU\S-1-5-21 removal for win 10

  • Open This PC, click View and select Options.
  • In the Folder Options window, choose View, select Show hidden files, folders, and drives, and then click OK.

Step 4.Find and delete suspicious files in the locations listed below:

%Temp%\[malware name]

%AppData%\[malware name]

%LocalAppData%\[malware name]

%LocalAppData%\[malware name].exe

%CommonAppData%\[malware name]



Virus and malware may hide its files in different locations of PC. If you are not able to locate files of HKU\S-1-5-21, you can try Wipersoft’s Malware Detection Tool to see if it will detect the unsafe files for you:

Download WiperSoft Anti-malware

Step 5. Find and remove nasty registry files related with HKU\S-1-5-21:

1. Open Registry Editor first:

  • Press Win [Windows key] + R on your keyboard.

uninstall HKU\S-1-5-21

  • Type regedit in the Run box and hit OK

eliminate HKU\S-1-5-21

2. Find out and remove all harmful registry files that may be related with HKU\S-1-5-21:

(Do Not Delete Any Registry File If You’re Not Familiar with It)

get rid of HKU\S-1-5-21


Wrong operation in Registry Editor might harm your computer.If you are not able to locate and identify the nasty registry files, we recommend using Wipersoft Anti-malware and see if it will find out unsafe registry files of infection for you. This may save you hours and avoid risks.

Download WiperSoft Anti-malware


Step 6. Reset Microsoft Edge, Chrome, Firefox and IE to remove HKU\S-1-5-21

Reset Microsoft Edge

remove HKU\S-1-5-21 from edge


1. Select More (…) on the address bar, then click Settings

2. click “Choose what to clear”

3. Select all the options and then click Clear button




Reset Chrome

remove HKU\S-1-5-21 from chrome

1. Open Chrome, then click “Customize and control Google Chrome” button >> click Settings

2. Scroll down to the bottom, then click on Show advanced settings button

3. After clicking on Show advanced settings button, scroll down to the bottom and click on Reset browser settings button

. A message box will pop up to inform that your browser settings will be restored to their original defaults, click Reset button when it appears:

Reset Firefox

remove HKU\S-1-5-21 from FIREFOX

1. Open Firefox, then click on Firefox button, then Click on Help button, then Click on Troubleshooting Information

2. At the Troubleshooting Information page, click on Reset Firefox

3. A message box will pop up to let you confirm that you want to reset Firefox to its initial state, click Reset Firefox button when it appears:

Reset Internet Explorer

remove HKU\S-1-5-21 from ie

1. Open Internet Explorer, then click on Tools, then click on Internet Options

2. On the Internet Options window: click on Advanced tab, then click Reset button

3. A message box will pop up to let you confirm that you want to reset all Internet Explorer Settings, click Reset button when it appears:

4. When the resetting process is done, you’ll see this message box, click Close

5. You’ll need to restart your Internet Explorer to complete the resetting process.

Tips for Threat Prevention

– Always running professional Antivirus or Antimalware and keep Firewall ON;

– Create System Restore Point regularly and back up important personal files;

– Avoid downloading free programs from unknown third party shared sites;

– Regularly update system via automatic system update;

– Don’t access porn sites or similar sites which are potentially harmful;

– Avoid opening any attachments of unknown emails.