How to completely remove Trojan.Zeroaccess!inf4 (Virus Removal Guide)

If Norton Internet Security or Norton Antivirus has found a Trojan.Zeroaccess!inf4 infection, then your computer is infected with a ZeroAccess rootkit.
[Image: Trojan.Zeroaccess!inf4 virus]
The Trojan.Zeroaccess!inf4 is a dangerous threat that has been circulating for several years. In the time that Sirefef 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.

Primarily, Trojan.Zeroaccess!inf4 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!inf4 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!inf4 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!inf4 may also be dropped or installed by other malware, including variants of the Trojan:Win32/Necurs family.

In the wild, newer Trojan.Zeroaccess!inf4 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”)

Trojan.Zeroaccess!inf4 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.

How to remove Trojan.Zeroaccess!inf4 virus (Virus Removal Guide)

This malware removal guide may appear overwhelming due to the amount of the steps and numerous programs that are being used. We have only written it this way to provide clear, detailed, and easy to understand instructions that anyone can use to remove malware for free.
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.

STEP 1:  Use ESETSirfefCleaner tool to remove Trojan.Zeroaccess!inf4

In this first step, we will use the ESETSirefefCleaner tool to remove the Trojan.Zeroaccess!inf4 from your computer.

  1. You can download ESETSirefefCleaner from the below link.
    ESETSIREFEFCLEANER DOWNLOAD LINK(This link will automatically download ESETSirfefCleaner on your computer.)

    Unable to download “ESETSirefefCleaner.exe contained a virus and was deleted”.
    More recent variants of Sirefef might prevent you from downloading this removal tool. If you cannot download the tool, follow the steps below:

    1. Click Start → Computer → Local Disk (C:) → Program Files.
    2. Right-click the Windows Defender folder and select Rename from the context menu.
    3. Add a unique variation to the filename, such as .old (for example, Windows Defender.old).
    4. Click the link above to download the ESETSirefefCleaner tool.When the download is complete, make sure to rename the Windows Defender folder back to its original filename before running the ESET SirefefCleaner tool.
  2. Double-click on ESETSirefefCleaner.exe to start this utility. You may be presented with an User Account Control pop-up asking if you want to allow this to make changes to your device. If this happens, you should click “Yes” to continue.
  3. The message “Win32/Sirefef.EV found in your system” will be displayed if an infection is found. To remove Trojan.Zeroaccess!inf4 from your computer, press the Y key on your keyboard
    ESETSirefefCleaner virus detected
  4. Once the tool has run, you will be prompted to restore system services after you restart your computer. Press Y on your keyboard to restore system services and restart your computer.
    ESETSirefefCleaner Press Y to remove malware
  5. Once your computer has restarted, if you are presented with a security notification click Yes or Allow. and then continue wit the next step.

STEP 2: Use RKill to stop the Trojan.Zeroaccess!inf4 malicious processes

RKill is a program that will attempt to terminate all malicious processes associated with Trojan.Zeroaccess!inf4, so that we will be able to perform the next step without being interrupted by this malicious software.

Because this utility will only stop Trojan.Zeroaccess!inf4 running process and does not delete any files, after running it you should not reboot your computer as any malware processes that are configured to start automatically will just be started again.
  1. You can download Rkill from the below link.
    RKILL DOWNLOAD LINK (his link will open a new web page from where you can download “RKill”)
  2. Double click on Rkill program to stop the malicious programs from running.
    Start the Rkill program
  3. RKill will now start working in the background, please be patient while this utiltiy looks for malicious process and tries to end them.
    Rkill Running
  4. When the Rkill tool has completed its task, it will generate a log. Do not reboot your computer after running RKill as the malware programs will start again.
    Rkill Program


STEP 3: Scan your computer with Malwarebytes Anti-Malware to remove Trojan.Zeroaccess!inf4

Malwarebytes Anti-Malware is a powerful on-demand scanner which should remove the Trojan.Zeroaccess!inf4 virus from your machine. It is important to note that Malwarebytes Anti-Malware will run alongside antivirus software without conflicts.

  1. 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”)
  2. When Malwarebytes has finished downloading, double-click on the “mb3-setup-consumer” file to install Malwarebytes Anti-Malware on your computer.
    Malwarebytes installer
    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.
    Malwarebytes User Account Control Prompt
  3. When the Malwarebytes installation begins, you will see the Malwarebytes Setup Wizard which will guide you through the installation process.
    Setup Malwarebytes installer
    To install Malwarebytes Anti-Malware on your machine, keep following the prompts by clicking the “Next” button.
    Completing the Malwarebytes Setup Wizard
  4. Once installed, Malwarebytes will automatically start and update the antivirus database. To start a system scan you can click on the “Scan Now” button.
    Perform a system scan with Malwarebytes
  5. 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.
    Malwarebytes scanning for malware
  6. 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 Quarantine Selected
  7. 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.
    Malwarebytes removing malware from computer
    When the malware removal process is complete, you can close Malwarebytes Anti-Malware and continue with the rest of the instructions.

STEP 4: 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.

  1. 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”)
  2. When HitmanPro has finished downloading, double-click on the “hitmanpro” file to install this program on your computer.
    HitmanPro icon
    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.
    HitmanPro User Account Control Pop-up
  3. 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 setup process
  4. HitmanPro will now begin to scan your computer for malware.
    HitmanPro scanning for Trojan.Zeroaccess!inf4 virus
  5. 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.
    HitmanPro detected malware
  6. Click on the “Activate free license” button to begin the free 30 days trial, and remove all the malicious files from your computer.
    Activate HitmanPro to remove malware
    When the process is complete, you can close HitmanPro and continue with the rest of the instructions.

(OPTIONAL) STEP 5: Use Zemana AntiMalware Portable to remove Trojan.Zeroaccess!inf4

Zemana AntiMalware Portable is a free utility that will scan your computer for the Trojan.Zeroaccess!inf4 and other malicious programs.
This step should be performed only if your issues have not been solved by the previous steps.
  1. 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”)
  2. Double-click on the file named “Zemana.AntiMalware.Portable” to perform a system scan with Zemana AntiMalware Free.
    Zemana AntiMalware portable
    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.
    Zemana AntiMalware User Account Control
  3. When Zemana AntiMalware will start, click on the “Scan” button to perform a system scan.
    Zemana AntiMalware Free Scan
  4. Zemana AntiMalware will now scan your computer for malicious programs. This process can take up to 10 minutes.
    Zemana AntiMalware scanning for virus
  5. 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 Removing Trojan.Zeroaccess!inf4 Virus
    Zemana AntiMalware will now start to remove all the malicious programs from your computer.
Your computer should now be free of the Trojan.Zeroaccess!inf4. If you are still experiencing problems while trying to remove Trojan.Zeroaccess!inf4 from your machine, you can ask for help in our Malware Removal Assistance forum.

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STELIAN PILICI
I've started MalwareTips in 2010 to help people solve their computer problems. 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.

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