Remove Trojan ZeroAccess virus (Removal Guide)

The ZeroAccess trojan is a dangerous threat that has been circulating for several years. In the time that ZeroAccess has been in the wild there have been a number of revisions, with modifications to its functionality, infection strategy and its persistence mechanisms on an infected machine. However, the core purpose has remained: to assume full control of the machine by adding it to the ZeroAccess botnet and to monetize the new asset by downloading additional malware.
[Image: Trojan.Zeroaccess!inf4 (Norton)]
Primarily, Trojan ZeroAccess is a kernel-mode rootkit, similar in ethos to the TDL family of rootkits. It uses advanced techniques to hide its presence, is capable of functioning on both 32 and 64-bit flavors of Windows from a single installer, contains aggressive self defense functionality and acts as a sophisticated delivery platform for other malware.

Trojan ZeroAccess remains hidden on an infected machine while downloading more visible components that generate revenue for the botnet owners. Currently the downloaded malware is mostly aimed at sending spam and carrying out click fraud, but previously the botnet has been instructed to download other malware and it is likely that this will be the case again in the future.

Trojan ZeroAccess has been observed being distributed by exploits and programs that promote software-piracy, such as ‘keygens’ and ‘cracks’ (programs designed to bypass software licensing).

Variants of Trojan ZeroAccess may also be dropped or installed by other malware, including variants of the Trojan:Win32/Necurs family.

In the wild, newer Trojan ZeroAccess variants have been observed dropping the following two files to a chosen directory, for example, C:\recycler\s\:

  • “@” – this file contains information that Sirefef can use to find other infected computers
  • “n” – this file contains the malicious code for peer-to-peer (P2P) communication

These newer variants then make the following changes to the registry to ensure that Sirefef runs each time you start your computer:

In subkey: HKLM\Software\Classes\clsid\{5839fca9-774d-42a1-acda-d6a79037f57f}\InprocServer32
Modifies value: “(Default)”
From data: “\wbem\wbemess.dll”
With data: “” (for example, “c:\recycler\s\\n”)

In the wild, the Trojan ZeroAccess may be detected by antivirus products as:

  • Win64/Sirefef.W (ESET)
  • ZeroAccess.BX (AVG)
  • Win64/Sirefef.AE (ESET)
  • Trojan.Zeroaccess.B (Ikarus)
  • ZeroAccess.C (McAfee)
  • HEUR.Backdoor.Win64.Generic (Kaspersky)
  • Troj/Sirefef-AQ (Sophos)
  • Trojan.Zeroaccess!inf2 (Symantec)
  • Trojan:Win32/Sirefef (Microsoft)
  • W32/Troj_Generic.UUZF (Norman)
  • Rootkit.ZeroAccess.Gen.4 (VirusBuster)
  • Trojan horse Crypt.AQLW (AVG)
  • TR/Sirefef.BV.2 (Avira)
  • Trojan.Sirefef.BV (BitDefender)
  • BackDoor.Maxplus.3710 (Dr.Web)
  • Trojan.Sirefef.C (Ikarus)
  • ZeroAccess.B (McAfee)
  • Troj/ZAccess-AH (Sophos)
  • Trojan.Zeroaccess!inf4 (Norton)
  • TROJ_ZACCESS.CQJ (Trend Micro)

Trojan ZeroAccess is a dangerous threat that uses advanced stealth techniques in order to hinder its detection and removal. As a consequence of being infected with this threat, you may need to repair and reconfigure some Windows security features.

Because the malware removal process for the ZeroAccess trojan is very complex, we recommend that you backup your personal files and folders before starting to remove this infection.

Trojan ZeroAccess – Virus Removal Guide

STEP 1:  Remove Trojan ZeroAccess infection with Kaspersky TDSSKiller

As part of its self defense mechanism, Trojan ZeroAccess will install a rootkit on the infected computer.In this first step, we will run a system scan with Kaspersky TDSSKiller to remove this rookit.

  1. Please download the latest official version of Kaspersky TDSSKiller.
    KASPERSKY TDSSKILLER DOWNLOAD LINK(This link will automatically download Kaspersky TDSSKiller on your computer.)
  2. Before you can run Kaspersky TDSSKiller, you first need to rename it so that
    you can get it to run. To do this, right-click on the TDSSKiller.exe icon and select Rename.
    Edit the name of the file from TDSSKiller.exe to iexplore.exe, and then double-click on it to launch.
  3. Kaspersky TDSSKiller will now start and display the welcome screen and we will need to click on Change Parameters.
    Kaspersky TDSSKiller change settings
  4. In the new open window,we will need to enable Detect TDLFS file system, then click on OK.
    Kaspersky TDSSKiller Detect TDLFS file system
  5. Next,we will need to start a scan with Kaspersky, so you’ll need to press the Start Scan button.
    Kaspersky TDSSKiller start scan
  6. Kaspersky TDSSKiller will now scan your computer for Trojan ZeroAccess infection.
    Kaspersky TDSSKiller scan
  7. When the scan has finished it will display a result screen stating whether or not the infection was found on your computer. If it was found it will display a screen similar to the one below.
    Kaspersky TDSSKiller results
  8. To remove the infection simply click on the Continue button and TDSSKiller will attempt to clean the infection.A reboot will be require to completely remove any infection from your system.

STEP 2 : Remove the malicious files and replace the infected services.exe file

Trojan ZeroAccess may infect your Windows services, so we will need to run Combofix to replace these files.

  1. Download Combofix from any of the below links.
    COMBOFIX DOWNLOAD LINK #1 (This link will automatically download Combofix on your computer)
    COMBOFIX DOWNLOAD LINK #2  (This link will automatically download Combofix on your computer)
  2. Before running this utiltiy,please follow the below instructions:
    • Close any open browsers.
    • Close/disable all anti virus and anti malware programs so they do not interfere with the running of ComboFix.
      Temporarily disable your anti-virusscript blocking and any anti-malware real-time protection beforeperforming a scan. They can interfere with ComboFix or remove some of its embedded files which may cause “unpredictable results”.
    • WARNING: Combofix will disconnect your machine from the Internet as soon as it starts
      Please do not attempt to re-connect your machine back to the Internet until Combofix has completely finished.
      If there is no internet connection after running Combofix, then restart your computer to restore back your connection.
  3. Start the Combofix scan:
    1. Double click on ComboFix.exe and then follow the prompts.
    2. Accept the disclaimer and allow to update if it asks.
    3. When finished, it shall produce a log for you.
    4. Restart your computer

    Additional Notes:

    • DO NOT mouse-click Combofix’s window while it is running. That may cause it to stall.
    • DO NOT “re-run” Combofix. If you have a problem, reply back for further instructions.
    • IF after the reboot you get errors about programs being marked for deletion then reboot, that will cure it.

STEP 3 : Remove the malicious registry keys added by the Trojan ZeroAccess

Trojan ZeroAccess has added some malicious registry keys to your Windows installation, to remove them we will need to perform a scan with RogueKiller.

  1. You can download RogueKiller from the below link.
    ROGUEKILLER DOWNLOAD LINK (This link will automatically download RogueKiller on your computer)
  2. Double click on RogueKiller.exe to start this utility and then wait for the Prescan to complete.This should take only a few seconds and then you can click the Start button to perform a system scan.
    [Image: RogueKiller while scanning]
  3. After the scan has completed, press the Delete button to remove any malicious registry keys.
    [Image: RogueKiller removing Trojan ZeroAccess]

STEP 4: Remove Trojan ZeroAccess malicious files with Malwarebytes Anti-Malware

Malwarebytes Chameleon technologies will allow us to install and run a Malwarebytes Anti-Malware scan without being blocked by Trojan ZeroAccess.

  1. Download Malwarebytes Chameleon from the below link and extract it to a folder in a convenient location.
    MALWAREBYTES CHAMELEON DOWNLOAD LINK  (This link will open a new web page from where you can download Malwarebytes Chameleon)
  2. Make certain that your infected computer is connected to the internet and then open the Malwarebytes Chameleon folder and double-click on svchost.exe.
    Malwarebytes Chameleon
    IF Malwarebytes Chameleon will not open, double-click on the other renamed files until you find one will work, which will be indicated by a black DOS/command prompt window.
  3. Follow the onscreen instructions to press a key to continue and Chameleon will proceed to download and install Malwarebytes Anti-Malware for you.
    Malwarebytes Chameleon press key
  4. Once it has done this, it will update Malwarebytes Anti-Malware, and you’ll need to click OK when it says that the database was updated successfully.
    Malwarebytes Chameleon updating its database
  5. Malwarebytes Anti-Malware will now attempt to kill all the malicious process associated with Trojan ZeroAccess.Please be aware that this process can take up to 10 minutes, so please be patient.
    Malwarebytes Chameleon killing malware
  6. Next, Malwarebytes Anti-Malware will automatically open and perform a Quick scan for Trojan ZeroAccess malicious files as shown below.
    [Image: Malwarebytes Anti-Malware scanning for Trojan ZeroAccess]
  7. Upon completion of the scan, click on Show Result
    [Image: Malwarebytes Anti-Malware scan results]
  8. You will now be presented with a screen showing you the malware infections that Malwarebytes Anti-Malware has detected.
    Make sure that everything is Checked (ticked),then click on the Remove Selected button.
    [Image:Malwarebytes removing virus]
  9. After your computer restarts, open Malwarebytes Anti-Malware and perform a Full System scan to verify that there are no remaining threats

STEP 5: Remove Trojan ZeroAccess rootkit with HitmanPro

  1. you can download HitmanPro from the below link,then double click on it to start this program.
    HITMANPRO DOWNLOAD LINK (This link will open a new web page from where you can download HitmanPro)
    IF you are experiencing problems while trying to start HitmanPro, you can use the Force Breach mode.To start HitmanPro in Force Breach mode, hold down the left CTRL-key when you start HitmanPro and all non-essential processes are terminated, including the malware process. (How to start HitmanPro in Force Breach mode – Video)
  2. HitmanPro will start and you’ll need to follow the prompts (by clicking on the Next button) to start a system scan with this program.
    HitmanPro scanner
    HitmanPro installation
  3. HitmanPro will start scanning your computer for Trojan ZeroAccess malicious files as seen in the image below.
    HitmanPro scan after Win 7 Defender
  4. Once the scan is complete,you’ll see a screen which will display all the infected files that this utility has detected, and you’ll need to click on Next to remove this malicious files.
    HitmanPro scan results
  5. Click Activate free license to start the free 30 days trial and remove all the malicious files from your computer.
    HitmanPro 30 days activation button

STEP 6: Double check for any left over infections on your computer

If want to make another check for any left over malicious files, you can run a scan with the following tools:

STEP A: Run a scan with Eset Online Scanner.

  1. Download ESET Online Scanner utility.
    ESET Online Scanner Download Link (This link will automatically download ESET Online Scanner on your computer.)
  2. Double click on the Eset installer program (esetsmartinstaller_enu.exe).
  3. Check Yes, I accept the Terms of Use
  4. Click the Start button.
  5. Check Scan archives
  6. Push the Start button.
  7. ESET will then download updates for itself, install itself, and begin scanning your computer. Please be patient as this can take some time.
  8. When the scan completes, push Finish

STEP B: Run a scan with Emsisoft Emergency Kit.

  1. Please download the latest official version of Emsisoft Emergency Kit.
    EMSISOFT EMERGENCY KIT DOWNLOAD LINK (This link will open a download page in a new window from where you can download Emsisoft Emergency Kit)
  2. After the download process will finish , you’ll need to unpack EmsisoftEmergencyKit.zip and then double click on EmergencyKitScanner.bat
  3. A pop-up will prompt you to update Emsisoft Emergency Kit , please click the “Yes” button.After the Update process has completed , put the mouse cursor over the “Menu” tab on the left and click-on “Scan PC“.
  4. Select “Smart scan” and click-on the below “SCAN” button.When the scan will be completed , you will be presented with a screen showing you the malware infections that Emsisoft Emergency Kit has detected.Make sure that everything is Checked (ticked) and click on the ‘Quarantine selected objects‘ button.

Next,we will remove Combofix from your machine and in addition, you can uninstall any of the tools that we’ve used:

Lets remove ComboFix from your computer:

  1. Hold down the Windows key + R on your keyboard. This will display the Run dialogue box
  2. In the Run box, type in ComboFix /Uninstall (Notice the space between the “x” and “/”) then click OK Combofix uninstall command
  3. Follow the prompts on the screen
  4. A message should appear confirming that ComboFix was uninstalled

Delete the following files: (If they exist)
C:\ComboFix.txt

Delete the following folders: (If they exist)
C:\ComboFix
C:\Qoobox
ESET Online Scanner, Emsisoft Emergency Kit, Kaspersky TDSSKiller and RogueKiller can be removed by right clicking on their icons, and selecting Delete.
We strongly recommend that you keep Malwarebytes Anti-Malware and HitmanPro installed on your machine and perform regular scans with these on-demand scanners. However if you wish to remove them, you can go into the Add/Remove Programs and uninstall these two utilities.

If you are still experiencing problems while trying to remove ZeroAccess trojan from your machine, please start a new thread in our Malware Removal Assistance forum.

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ABOUT STELIAN PILICI

I am the creator and owner of MalwareTips.com.
My area of expertise includes malware removal and computer forensics. I'm active in the various online anti-malware communities where I do researches for new malware threats as they are released.
I live in Bucharest (Romania), where I run my own local computer repair shop.
I repair both hardware and other operating systems related issues, however most of my business is malware related problems.

You can follow me on Google+ and I will keep you up-to-date with the latest computer infections and malware threats.

  • Chris

    You’re a lifesaver! I didn’t realise how open my laptop was to threats and now I’m going to make sure it doesn’t happen again =)

  • Kevin

    Stelian – Thank you. I used your instructions, and they worked perfectly to fix my issue. Could only make a small donation at this time, but hopefully I can send you a little more in the future. What you do is a great service to community.

  • Adriian

    I’d just like to say that I have not had the opportunity to follow this guide, but I DO know that simply using bootable CDs from symmantec and kaspersky, and the bootable removal tools provided by symmantec and mcafee, are not sufficient. I’m going to follow this guide and report the results. Thanks so much for the time you spent creating the massive and easy to understand guide.

  • http://malwaretips.com/ Stelian Pilici

    Hello,
    Yes, you should uninstall Combofix as it’s an advance utility which needs to be used only in some very rare cases.
    Stay safe!

  • http://malwaretips.com/ Stelian Pilici

    Hello Ralph,
    This is one of the most agressive forms of malware for Windows. It will corrupt critical files, stop Windows process and other kinds of malicious behavior.
    Usually to remove malware from Windows you will need to run a utility or two, however this infection is one of the worst.

  • http://malwaretips.com/ Stelian Pilici

    Hello,
    Download again TDSSkiller, and this time do not rename it. If you will still experience this issue, go ahead with the other steps.
    Stay safe!

  • Charles

    I have a question, Norton Anti-Virus blocked this Trojan, but it still gives me messages that I have it, but Norton still keeps blocking it, I ran the first step, but it says there was no rootkit, is this a good or bad thing?

    • http://malwaretips.com/ Stelian Pilici

      Hello.
      Can you show me a screenshot of the alert or the path that Norton is saying that is infected.

      Stay safe!

  • tanku

    thanks for all your effort in putting all of this together. I certainly benefited from it.

  • Shelley

    Thank you for the help. I was finally able to remove the file with HitmanPro. The error messages from the virus have been driving my husband crazy. We are glad to have them gone!

  • SteveComp2

    Hi Stelian-

    My McAfee security package failed in both protecting me from what it identifies as zeroaccess, I am also unable to download the McAfee removal tool. I get a Windows labeled download message telling me that the removal tool has a virus and has been deleted. I find your site and try to download the Kaspersky TDSS Killer and I get the same result. The file is deleted as soon as it is downloaded. How do I implement your removal strategy if I am unable to download the tools and what can I do to enable the downloading of these applications. Thanks in advance.