Trojan.Zeroaccess.B is a computer Trojan that employs advance rootkit techniques to hide its presence from compromised PC. The threat also creates a number of hidden system files and infects Windows driver files.

Typically, this kind of Trojan may infiltrate a computer when it sees security vulnerabilities. By exploiting that weaknesses, Trojan.Zeroaccess.B may gain access and starts to modify various system settings. Its effect on 32-bit and 64-bit systems is different. The Trojan tends to infect a driver file and append it with own code. It usually targets files from \Drivers\classpnp.sys to %System%\Drivers\win32k.sys if they are listed in alphabetical order.

While on 64-bit machine, Trojan.Zeroaccess.B will create the following categories if not found:
%Windir%\assembly\GAC_64
%Windir%\assembly\GAC_32
%Windir%\assembly\GAC_MSIL
%Windir%\assembly\tmp\U

Next, the Trojan drops and loads files, create an event, and modify a number of registry entries. It also ends a service named MpsSvc. It is a Windows component and part of Windows Firewall, which protects the computers by blocking illegal Internet traffics.

Trojan.Zeroaccess.B also communicates to a remote host via peer-to-peer connection and downloads a number of files in the format of 800000xx. Where ‘xx’ is a value that refers to a combination of letters or numbers. Files downloaded into the computer contain various payloads. One file is meant to send an HTTP request to a remote host. Another one may attempt to inject malicious code into service.exe or svchost.exe process of Windows. Other components of Trojan.Zeroaccess.B can open a backdoor, connects to certain location, and waits for command from a remote attacker.

Type Trojan
Sub-Type Rootkit
OS Affected Windows XP, Windows Vista, Windows 7

What are the Symptoms of Trojan.Zeroaccess.B Infection?

There are no common symptoms generates by this threat aside from a warning message that will come from your antivirus program.

Trojan.Zeroaccess.B Detection by Symantec

The threat will drop the following malicious files:
%Windir%\assembly\tmp\{1B372133-BFFA-4dba-9CCF-5474BED6A9F6}
%System%\consrv.dll
%Windir%\assembly\tmp\U\80000000.@
%Windir%\assembly\tmp\U\800000cb.@
%Windir%\assembly\tmp\U\800000cf.@
%Windir%\assembly\tmp\U\80000016.@
%Windir%\assembly\tmp\U\80000032.@
%Windir%\assembly\tmp\U\80000064.@

Follow these Procedures to Remove Trojan.Zeroaccess.B

Procedure 1: Start Computer in Safe Mode

1. Restart your computer in Safe Mode with Networking

- To run Windows system in Safe Mode, please press F8 after turning ON the computer. Hit the keyboard button before the appearance of Windows logo. If successful, you will see a screen of Windows Advanced Options Menu. See image below for your reference. This area will allow you to choose preferences on how you want to boot the system.

- From the selections, choose Safe Mode with Networking. Please use keyboard's arrow up/down to navigate between selections and press Enter on the keyboard to proceed. Keep in mind that booting Windows in Safe Mode only loads minimum driver files. Thus, most of the devices will not be available on this mode. Seeing pixilated images on the screen is normal since your current resolution is set to low.

SafeMode Networking

Procedure 2: Scan and remove Trojan.Zeroaccess.B files with MalwareBytes Anti-Malware

To remove Trojan.Zeroaccess.B, download Malwarebytes Anti-Malware by clicking on the button below. This tool is effective in getting rid of Trojans, viruses and malware.

Download Trojan.Zeroaccess.B Removel Tool

1. After downloading, please install the program using the default settings.
2. At the end of the installation, please make sure that it will download necessary updates.
3. Once update has completed. The tool will launch.
4. Thoroughly scan the computer and remove all threats detected by this anti-malware program.

Procedure 3: Run Symantec's ZeroAccess Fix Tool to remove Trojan.Zeroaccess.B components.

This tool from Symantec can remove infections of Trojan.Zeroaccess.B as well as other variants of the same nature.

1. Click on the button below to download ZeroAccess Fix Tool. Save the file FixZeroAccess.exe to your desktop or any convenient location.

Download FixZeroAccess

2. You need to close any running programs before running this tool.
3. Turn OFF System Restore if you are using Windows XP. Trojan.Zeroaccess.B files may hide some of its components on system restore files.
4. Next, browse the folder where you saved the file FixZeroAccess.exe. Double-click on it to initiate the tool. To run the file in Windows Vista and Windows 7, right-click on it and choose 'Run as administrator' from the selection.

Icon of ZeroAccessFix Run As Administrator

5. It will display End User License Agreement (EULA), please click on I accept to use the program.
6.Click on Proceed to begin the removal process, let the tool to run and do its course.
7. If it requires you to restart Windows, please do so. This method may remove Trojan.Zeroaccess.B components such as files and hidden modules.

Restart Windows

8. When Windows starts, ZeroAccess Fix Tool will provide some details of the infection.
9. If it prompts for update, you need to run LiveUpdate to make sure that it contains the most recent virus definitions.
10. Wait for the tool to complete the scan process. When done, it will issue a message and specify identified threats. These threats are removed during the scan process, so, there is no need to worry about their presence.

Procedure 4: Make sure that Trojan.Zeroaccess.B is 100% deleted with Avast aswMBR

A Trojan often drops malware using an advance technology known as rootkit. It hides the installation of Trojan.Zeroaccess.B from your anti-virus program and injects malicious code to running Windows processes. To complete the clean-up process, you also need to scan and remove rootkit Trojan.

1. Download aswMBR from Avast server. Save it to your computer.

Avast Rootkit Scanner

2. Double-click on the file aswMBR.exe to run the program.
3. If it prompts you to download the latest Avast! virus definition, please click Yes. This is necessary to identify most recent version of the Trojan as well as hidden files of Trojan.Zeroaccess.B.

Updating aswMBR

4. Click on Scan button to start checking your computer for presence of rootkit Trojan and other viruses. It will display a message "Scan finished successfully" when done.

aswMBR Scan

5. Click Fix or FixMBR to start removing infection. If aswMBR contains the latest Avast! virus definition file, it will automatically clean infected files on your PC.

Protect your PC from Trojan.Zeroaccess.B or Similar Attack

Turn On Security Features of your Internet Browser

Internet Explorer - Activate SmartScreen Filter

Internet Explorer versions 8 and 9 has this feature called SmartScreen Filter. It helps detect phishing web sites and protect you from downloading malicious files online. You may have avoided Trojan.Zeroaccess.B virus if this has been active on your PC. To turn on SmartScreen Filter, follow these steps:

1. Please open Internet Explorer.
2. On top menu, select Tools (IE 9). For IE 8, please look for Safety menu.
3. Select SmartScreen Filter from the drop-down list and click on Turn on SmartScreen Filter.

IE SmartScreen Filter

4. Please restart Internet Explorer.

Google Chrome's Enable Phishing and Malware Protection

With Google Chrome's Phishing and Malware Detection feature, you will have lesser risks browsing the web. It will display a warning when the site you are trying to visit is suspicious. To enable Phishing and Malware Protection, please do these steps:

1. Open Google Chrome.
2. Click on the Customize and control Google Chrome (3-Bars Icon) located on top right corner of the browser.
3. Select Settings from the drop-down list.
4. Once on the settings page, click on Show advanced settings... at the bottom of the page to see the rest of the Chrome setup.
5. Locate Privacy section and mark 'Enable phishing and malware protection'.

Chrome Security Settings

6. Please restart Google Chrome. New settings keep your browser safe while surfing the web.

Mozilla Firefox - Block Attack Sites and Web Forgeries

Phishing and Malware Protection is a built-in feature on Firefox version 3 or later. It warns you when a page you are trying to visit contains phishing content or an attack site designed to drop threats on the computer. To help you keep safe while browsing the Internet using Firefox, please follow this guide:

1. Open Mozilla Firefox browser.
2. On top menu, click on Tools. Then select Options from the list.
3. Select Security and put a check mark on the following items:

  • Warn me when sites try to install add-ons
  • Block reported attack sites
  • Block reported web forgeries

Firefox Security Settings

Remove Trojan.Zeroaccess.B & Protect Your Computer Now!

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One thought on “Trojan.Zeroaccess.B

  • September 5, 2013 at 9:57 pm

    this is exactly my problem(32-bit), please does reinstalling windows fix the issue of this trojan because my avast detected the rootkit but it had infected a system file so i had to delete the file which led to other problems. will i be safe if i reinstall windows?

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