Discovered: July 13, 2011
Updated: November 29, 2013 11:16:11 AM
Type: Trojan
Infection Length: Varies
Systems Affected: Windows
CVE References: CVE-2006-0003 | CVE-2008-2992 | CVE-2009-0927 | CVE-2009-1671 | CVE-2009-1672 | CVE-2009-4324 | CVE-2010-1885

Trojan.Zeroaccess is a Trojan horse that uses an advanced rootkit to hide itself. It can also create a hidden file system, downloads more malware, and opens a back door on the compromised computer.

The Trojan is called ZeroAccess due to a string found in the kernel driver code that is pointing to the original project folder called ZeroAccess. It is also known as max++ as it creates a new kernel device object called __max++>.

Infection
This threat is distributed through several means. Some websites have been compromised, redirecting traffic to malicious websites that host Trojan.Zeroaccess and distribute it using the Blackhole Exploit Toolkit and the Bleeding Life Toolkit. This is the classic "drive-by download" scenario. It also updates itself through peer-to-peer networks, which makes it possible for the authors to improve it as well as potentially add new functionality.


Functionality
The primary motivation of this threat is to make money through pay per click advertising. It does this by downloading an application that conducts Web searches and clicks on the results. This is known as click fraud , which is a highly lucrative business for malware creators.

The threat is also capable of downloading other threats on to the compromised computer, some of which may be Misleading Applications that display bogus information about threats found on the computer and scare the user into purchasing fake antivirus software to remove the bogus threats. It is also capable of downloading updates of itself to improve and/or fix functionality of the threat.

It is also know to download software onto compromised computers in order to mine bitcoins for the malware creators. Bitcoin mining with a single computer is a futile activity, but when it is performed by leveraging the combined processing power of a massive botnet, the sums that can be generated is considerable.

Furthermore, it opens a back door and connects to a command and control (C&C) server, which allows the remote attacker access to the compromised computer. The attacker is then able to perform any number of actions on the computer, and the computer may then become part of a wider botnet.

It is able to achieve the above functions silently as it infects a system driver that acts as a rootkit hiding all of its components on the computer. The threat creates an encrypted hidden volume in the computer's file system where it stores all of its components. Not only does it store all of its components in the hidden volume, it can also hide any other malicious software that it downloads onto the computer there as well.


Link to Backdoor.Tidserv
There is strong evidence to suggest that there are link between Trojan.Zeroaccess and another malware with advanced rootkit capabilities, Backdoor.Tidserv . But whether the creators of the two malware are the same or not is not known. It is possible that the same person created the code for both pieces of malware and sold them to different gangs on the black market. Alternatively, it is possible that the creators of Zeroaccess bought the Tidserv code and modified it for their purposes. What is certain, however, is that Zeroaccess actively searches for any trace of Tidserv on the computer and removes it if it finds it.



GEOGRAPHICAL DISTRIBUTION
Symantec has observed the following geographic distribution of this threat.






PREVALENCE
Symantec has observed the following infection levels of this threat worldwide.




SYMANTEC PROTECTION SUMMARY
The following content is provided by Symantec to protect against this threat family.


Antivirus signatures



Antivirus (heuristic/generic)


Intrusion Prevention System

Antivirus Protection Dates

  • Initial Rapid Release version July 13, 2011 revision 016
  • Latest Rapid Release version December 07, 2018 revision 016
  • Initial Daily Certified version July 13, 2011 revision 024
  • Latest Daily Certified version December 08, 2018 revision 002
  • Initial Weekly Certified release date July 13, 2011

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Jarrad Shearer

Discovered: July 13, 2011
Updated: November 29, 2013 11:16:11 AM
Type: Trojan
Infection Length: Varies
Systems Affected: Windows
CVE References: CVE-2006-0003 | CVE-2008-2992 | CVE-2009-0927 | CVE-2009-1671 | CVE-2009-1672 | CVE-2009-4324 | CVE-2010-1885

1. Prevention and avoidance
1.1 User behavior and precautions
1.2 Patch operating system and software
1.3 Address blocking
2. Infection method
3. Functionality
3.1 System modifications
3.2 Network activity
3.3 Rootkit functionality
3.4 Command and control (C&C) server
3.5 Disables security software
4. Additional information



1. PREVENTION AND AVOIDANCE
The following actions can be taken to avoid or minimize the risk from this threat.


1.1 User behavior and precautions
Users can mitigate the risk of infection by being careful about clicking links found on websites, such as blogs and forums where there is potentially little control or quality checks on the content. Basic checks such as hovering with the mouse pointer over the link will normally show where the link leads to. Users can also check online Web site rating services, such as safeweb.norton.com , to see if the site is deemed safe to visit.

When performing searches in search engines, treat any results returned with caution and double-check them before following the links. If pop-up advertisements are displayed, do not click on them or follow any links within them.

Users should be wary of any sites or services offering free downloads of copyrighted content, such as music, videos, or cracked software. These are often booby-trapped with malicious software and are a known method by way of which this threat can spread. Promiscuous file-sharing may also increase the risk of compromise.


1.2 Patch operating system and software
Users are advised to ensure that their operating systems and any installed software are fully patched, and antivirus and firewall software are up to date and operational. Users are recommended to turn on automatic updates if available so that their computers can receive the latest patches and updates when they are made available.

This threat is known to be spread by through the Blackhole Exploit Toolkit and the Bleeding Life Toolkit, which exploits certain vulnerabilities. Installation of the following patches will reduce the risk to your computer:



1.3 Address blocking
Block access to the following addresses using a firewall, router or add entries to the local hosts files to redirect the following addresses to 127.0.0.1:
  • 69.176.14.76
  • 76.28.112.31
  • 24.127.157.117
  • 117.205.13.113
  • 200.59.7.216
  • 113.193.49.54


2. INFECTION METHOD
As this threat is a Trojan, by definition it doesn't actively spread by itself. Therefore, it needs to use other methods to arrive on a compromised computer. Most commonly, Zeroaccess is spread through websites that have been compromised and redirect traffic to a malicious website that then in turn distribute it using the Blackhole Exploit Toolkit and the Bleeding Life Toolkit. These toolkits then attempt to exploit various vulnerabilities to penetrate the computer and infect it with Zeroaccess.

It has also been observed updating itself through peer-to-peer networks. This allows the creators to continually improve functionality of the threat as well as potentially add new functionality.



3. FUNCTIONALITY

The primary motivation of this threat is to make money through pay per click advertising and bitcoin mining. It does this by downloading additional software that conducts Web searches and clicks on the results or mines bitcoins. It attempts to stay hidden and undetected for as long as possible to maximize revenue generation opportunity. It does this by employing advanced rootkit techniques that hide not only the threat itself, but also any other threats that Zeroaccess may download and install.

Furthermore, it opens a back door and connects to a command and control (C&C) server, which allows the remote attacker access to the compromised computer. The attacker is then able to perform any number of actions on the computer, and the computer may then become part of a wider botnet.

Note: Side effects created by associated threats are not included in this report.


3.1 SYSTEM MODIFICATIONS
The following side effects may be observed on computers compromised by members of threat family. It should be noted that as this threat uses advanced stealth techniques to hide itself, any system modifications may not be visible on the compromised computer except where specialist tools are used to reveal them.


Files/folders created
None


Files/folders deleted
None


Files/folders modified
A driver file that is located alphabetically between %System%\Drivers\classpnp.sys and %System%\Drivers\win32k.sys is overwritten with the Trojan's own code.


Registry subkeys/entries created
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\[FILE NAME OF INFECTED DRIVER]\"ImagePath" = "\*"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\[FILE NAME OF INFECTED DRIVER]\"Type" = "1"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\[FILE NAME OF INFECTED DRIVER]\"Start" = "3"


Registry subkeys/entries deleted
None


Registry subkeys/entries modified (final values given)
None


Processes
The threat injects its code into the following process:
Explorer.exe


3.2 NETWORK ACTIVITY
The threat may be controlled remotely by a command and control (C&C) server. In particular it may be instructed to download and install various other malware. Symantec has observed Trojan.Downbot , aka “Shady RAT,” and W32.Imaut being downloaded by Zeroaccess.

The threat may perform the following network activities.


Downloading
Zeroaccess may download and execute potentially malicious files. It also may download updates of itself through peer-to-peer networks. It has been observed downloading files from the following IP address:
193.105.154.40


Uploading
The threat has been observed contacting the following IP address:
  • 69.176.14.76
  • 76.28.112.31
  • 24.127.157.117
  • 117.205.13.113
  • 200.59.7.216
  • 113.193.49.54

Note: The IP addresses used by this threat change frequently and there is a possibility the threat contacts a large number of locations.

The Trojan may send requests to the following location:
counter.yadro.ru


Other network activity
The threat may also attempt to contact one of the following time servers:
  • ntp2.usno.navy.mil
  • ntp.adc.am
  • chronos.cru.fr
  • wwv.nist.gov
  • clock.isc.org
  • time.windows.com
  • time2.one4vision.de
  • time.cerias.purdue.edu
  • clock.fihn.net
  • ntp.duckcorp.org
  • ntp.ucsd.edu
  • ntp1.arnes.si
  • ntp.crifo.org
  • tock.usask.ca


3.3 Rootkit functionality
searches for a driver that is located alphabetically between %System%\Drivers\classpnp.sys and %System%\Drivers\win32k.sys and overwrites the file with its own code, saving the original driver file in another location. The Trojan intercepts all traffic and if an attempt to read or write the infected driver is intercepted, the rootkit fakes the file content by showing the original clean copy of the driver.

ZeroAccess sets up a new RC4 encrypted hidden volume in the computer's file system, which makes its files inside the encrypted volume totally inaccessible to the operating system. The rootkit also allows the threat to download other potentially malicious files and store them inside the hidden rootkit volume, so that they are also hidden from both the user and security software.


3.4 Command and control (C&C) server
The threat attempts to communicate with a predetermined list of C&C servers. It bypasses less intelligent firewalls and security software and sends an encrypted request to all the servers in the list through TCP port 13620.


3.5 Disables security software
The threat creates a fake process and when a security application attempts to access that process during a system scan, the threat stops the security application, which in turn causes the application to crash. The threat then modifies the security application settings so that it cannot run again unless the settings are restored to their default settings.



4. ADDITIONAL INFORMATION
For more information relating to this threat family, please see the following resources:

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

Writeup By: Jarrad Shearer

Discovered: July 13, 2011
Updated: November 29, 2013 11:16:11 AM
Type: Trojan
Infection Length: Varies
Systems Affected: Windows
CVE References: CVE-2006-0003 | CVE-2008-2992 | CVE-2009-0927 | CVE-2009-1671 | CVE-2009-1672 | CVE-2009-4324 | CVE-2010-1885

You may have arrived at this page either because you have been alerted by your Symantec product about this risk, or you are concerned that your computer has been affected by this risk.

Before proceeding further we recommend that you run a full system scan . If that does not resolve the problem you can try one of the options available below.



FOR NORTON USERS
If you are a Norton product user, we recommend you try the following resources to remove this risk.

Removal Tool


If you have an infected Windows system file, you may need to replace them using from the Windows installation CD .


How to reduce the risk of infection
The following resources provide further information and best practices to help reduce the risk of infection.


FOR BUSINESS USERS
If you are a Symantec business product user, we recommend you try the following resources to remove this risk.

Identifying and submitting suspect files
Submitting suspicious files to Symantec allows us to ensure that our protection capabilities keep up with the ever-changing threat landscape. Submitted files are analyzed by Symantec Security Response and, where necessary, updated definitions are immediately distributed through LiveUpdate™ to all Symantec end points. This ensures that other computers nearby are protected from attack. The following resources may help in identifying suspicious files for submission to Symantec.


Removal Tool

If you have an infected Windows system file, you may need to replace them using from the Windows installation CD .


How to reduce the risk of infection
The following resource provides further information and best practices to help reduce the risk of infection.
Protecting your business network



MANUAL REMOVAL
The following instructions pertain to all current Symantec antivirus products.

1. Performing a full system scan
How to run a full system scan using your Symantec product


2. Restoring settings in the registry
Many risks make modifications to the registry, which could impact the functionality or performance of the compromised computer. While many of these modifications can be restored through various Windows components, it may be necessary to edit the registry. See in the Technical Details of this writeup for information about which registry keys were created or modified. Delete registry subkeys and entries created by the risk and return all modified registry entries to their previous values.


3. Restore detected files using the Windows Recovery Console in Windows XP
Since this threat modifies or replaces system files, it is necessary to recover the affected files using the Windows Recovery Console. To do this it is necessary to restart the computer and run the Windows Recovery Console. For full details on how to do this please read the Microsoft Knowledge Base article, How to install and use the Recovery Console in Windows XP .
  1. Insert the Windows XP CD-ROM into the CD-ROM drive.
  2. Restart the computer from the CD-ROM drive.
  3. Press R to start the Recovery Console when the "Welcome to Setup" screen appears.
  4. Select the installation that you want to access from the Recovery Console.
  5. Enter the administrator password and press Enter.
  6. To restore files detected as Trojan.Zeroaccess!inf, Trojan.Zeroaccess!inf2, or Trojan.Zeroaccess!inf3, type the following commands and press Enter after each command:

    • cd %System%\drivers [SYS FILES]
    • expand [CD/DVD DRIVE]:\i386\[DETECTED FILE NAME].[dl or sy]_

      For example:

      cd c:\windows\system32\drivers
      expand d:\i386\atapi.sy_

  7. Repeat the above step for each SYS or DLL file affected.
  8. Type exit.
  9. Press Enter. The computer will now restart automatically.

4. Restore detected files using System Recovery Options in Windows Vista/7
Since this threat modifies or replaces system files, it is necessary to recover the affected files using the System Recovery Options. To do this it is necessary to restart the computer and run the System Recovery Options. For full details on how to do this please read What are the system recovery options in Windows Vista or What are the system recovery options in Windows 7 .
  1. Restart the computer.
  2. As the computer restarts, press F8 repeatedly until the Advanced Boot Options screen appears.
  3. Select Repair Your Computer and press Enter.
  4. Select the keyboard input method and click Next.
  5. Select an administrator account, enter your password, and click OK.
  6. On the System Recovery Options menu, click Command Prompt.
  7. To restore files detected as Trojan.Zeroaccess!inf, Trojan.Zeroaccess!inf2, or Trojan.Zeroaccess!inf3, type the following commands and press Enter after each command:

    For users with a Windows Vista/7 disk or recovery disk
    Insert the disk into the CD/DVD drive

    • cd %System%\drivers [SYS FILES]
    • expand [CD/DVD DRIVE]:\Windows\[DETECTED FILE NAME].[dl or sy]_

      For example:
      cd c:\windows\system32\drivers
      expand d:\Windows\serial.sy_

    For users with a recovery partition
    Refer to your computer manufacturer's documentation for the location of the backup system files

    • cd %System%\drivers [SYS FILES]
    • expand [DRIVE LETTER]:\[SYSTEM FILES FOLDER]\[DETECTED FILE NAME].[dl or sy]_

      For example:
      cd c:\windows\system32\drivers
      expand f:\Windows\serial.sy_

  8. Repeat the above step for each SYS or DLL file affected.
  9. Close the Command Prompt window.
  10. Click Restart on the System Recovery Options menu. The computer will now restart.

Writeup By: Jarrad Shearer