Trojan:JS/Medfos.B is a malicious JavaScript file that redirects search queries when using websites such as AOL, Ask, Bing, Google and Yahoo to other website from which cyber criminals get some sort of revenue.
Medfos is a member of the Win32/Medfos family and got your computer, after you have visited an infected website which exploited a vulnerability from a Java or Adobe software and Medfos installed a file called chromeupdate.crx in your %LOCALAPPDATA% folder.
As part of its self-defense mechanism,once installed Medfos disguises itself as a legitimate Google Chrome or Firefox extension with the name ChromeUpdateManager 1.0 or Translate This 2.0, as show in the below images:
Trojan:JS/Medfos.B sole purpose is to generate revenue for its authors via pay-per-click advertising links and redirect traffic to affiliate sites, so we recommend that you remove this Trojan as soon as possible from your computer.
Always opt for the custom installation and deselect anything that is not familiar, especially optional software that you never wanted to download and install in the first place. It goes without saying that you should not install software that you don’t trust.
How to remove Trojan:JS/Medfos.B virus (Virus Removal Guide)
Please perform all the steps in the correct order. If you have any questions or doubt at any point, STOP and ask for our assistance.
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To remove Trojan:JS/Medfos.B virus, follow these steps:
- STEP 1: Use Zemana AntiMalware Portable to remove malware
- STEP 2: Scan and clean your computer with Malwarebytes Anti-Malware
- STEP 3: Double-check for malicious programs with HitmanPro
STEP 1: Use Zemana AntiMalware Portable to remove malware
Zemana AntiMalware Portable is a free utility that will scan your computer for the Trojan:JS/Medfos.B browser hijacker and other malicious programs.
- You can download Zemana AntiMalware Portable from the below link:
ZEMANA ANTIMALWARE PORTABLE DOWNLOAD LINK (This link will open a new web page from where you can download “Zemana AntiMalware Portable”) - Double-click on the file named “Zemana.AntiMalware.Portable” to perform a system scan with Zemana AntiMalware Free.
You may be presented with a User Account Control dialog asking you if you want to run this program. If this happens, you should click “Yes” to allow Zemana AntiMalware to run.
- When Zemana AntiMalware will start, click on the “Scan” button to perform a system scan.
- Zemana AntiMalware will now scan your computer for malicious programs. This process can take up to 10 minutes.
- When Zemana has finished finished scanning it will show a screen that displays any malware that has been detected. To remove all the malicious files, click on the “Next” button.
Zemana AntiMalware will now start to remove all the malicious programs from your computer. When the process is complete, you can close Zemana AntiMalware and continue with the rest of the instructions.
STEP 2: Scan and clean your computer with Malwarebytes Anti-Malware
Malwarebytes Anti-Malware is a powerful on-demand scanner which should remove the Trojan:JS/Medfos.B virus from your machine. It is important to note that Malwarebytes Anti-Malware will run alongside antivirus software without conflicts.
- You can download download Malwarebytes Anti-Malware from the below link.
MALWAREBYTES ANTI-MALWARE DOWNLOAD LINK (This link open a new page from where you can download “Malwarebytes Anti-Malware”) - When Malwarebytes has finished downloading, double-click on the “mb3-setup-consumer” file to install Malwarebytes Anti-Malware on your computer.
You may be presented with an User Account Control pop-up asking if you want to allow Malwarebytes to make changes to your device. If this happens, you should click “Yes” to continue with the installation.
- When the Malwarebytes installation begins, you will see the Malwarebytes Setup Wizard which will guide you through the installation process.
To install Malwarebytes Anti-Malware on your machine, keep following the prompts by clicking the “Next” button.
- Once installed, Malwarebytes will automatically start and update the antivirus database. To start a system scan you can click on the “Scan Now” button.
- Malwarebytes Anti-Malware will now start scanning your computer for malicious programs.
This process can take a few minutes, so we suggest you do something else and periodically check on the status of the scan to see when it is finished.
- When the scan has completed, you will be presented with a screen showing the malware infections that Malwarebytes Anti-Malware has detected.
To remove the malicious programs that Malwarebytes has found, click on the “Quarantine Selected” button.
- Malwarebytes Anti-Malware will now quarantine all the malicious files and registry keys that it has found.
To complete the malware removal process, Malwarebytes may ask you to restart your computer.
When the malware removal process is complete, you can close Malwarebytes Anti-Malware and continue with the rest of the instructions.
STEP 3: Double-check for malicious programs with HitmanPro
HitmanPro can find and remove malware, adware, bots, and other threats that even the best antivirus suite can oftentimes miss. HitmanPro is designed to run alongside your antivirus suite, firewall, and other security tools.
- You can download HitmanPro from the below link:
HITMANPRO DOWNLOAD LINK (This link will open a new web page from where you can download “HitmanPro”) - When HitmanPro has finished downloading, double-click on the “hitmanpro” file to install this program on your computer.
You may be presented with an User Account Control pop-up asking if you want to allow HitmanPro to make changes to your device. If this happens, you should click “Yes” to continue with the installation.
- When the program starts you will be presented with the start screen as shown below. Now click on the Next button to continue with the scan process.
- HitmanPro will now begin to scan your computer for malware.
- When it has finished it will display a list of all the malware that the program found as shown in the image below. Click on the “Next” button, to remove malware.
- Click on the “Activate free license” button to begin the free 30 days trial, and remove all the malicious files from your computer.
When the process is complete, you can close HitmanPro and continue with the rest of the instructions.



















Yep, finally! Thanks. MSE first identified and quarantined it, but couldn’t remove it. I tried the Malicious Software Tool, nuttin’. Malwarebytes, surprisingly, nuttin’. And MS Emergency Response Tool, nuttin’. None of those even saw it. Safe Mode boot, still none saw it. Skipped to Rogue Killer since most folks seemed to say that was the one…it identified two malicious entries which it highlighted red, the others were brown and clearly ok from what I could tell. Deleted the two reds, and we seem to be ok now.
Wow………. Thank you soooooooooooo much! What a great person to take the time to give such detailed instructions; complete with links for the program downloads! This was the ONLY site/instructions that worked on this virus!!!!! You are a life saver!!! THANK YOU THANK YOU!
At first I was skeptical that this page was an add for malware removal tools,lol. But scanning through the comments it seemed to be legit and not just marketing comments, so I gave it a try. Worked like a charm. Combofix, Roguekiller and Malwarebytes each found a few items, the other 3 scans had no results. Took about 3 hours, but these links and directions made it simple and a frustration free experience. Never removed a virus with so easy an experience. Thank you!!!! Erika
Thanks for the help, I ran all the programs and our Windows 7 computer is now clean. This was a hard one to handle, great web site and support.
Thanks for the instructions. Worked wonders. Get explanation on each step. This site rocks!
This did the trick. All the different stages worked fine. some took as long as 25 min, but the results are worth it. Thanks for giving me my computer back!
Thanks a combination of these software removed that annoying thing.
This worked a charm. Took a while, but it was well worth it. Thank you very much.
I could use a little more help. I ran the TDSSKiller–it didn’t find anything, so I moved on to the next step. The ComboFix seems to be “stuck” trying to create a new System Restore point. (left it overnight in case it was a slow process. . .found it in the same spot this morning. .. ). What do I do now?
Hello Patti,
Go ahead with the next step please.
Thank you for this! I was so worried I was going to have to spend a bunch of money and be without my work laptop. I followed your steps exactly and I dont know which step got rid of the problem, but my laptop is working as good as new now. Thank you SO much!
Tried lots of things until I found this processs. A little long but worked great.
Thank you so much for the simple and complete instructions. Since Kaspersky TDSSKiller didn’t find anything I used RKill instead, it did stop some processes. This trojan was really persistant so thanks again.