1. Symantec/
  2. Security Response/
  3. Backdoor.Winnti


Risk Level 1: Very Low

October 27, 2011
April 12, 2013 2:42:39 AM
Also Known As:
Troj/Winnti-B [Sophos]
Systems Affected:
Windows 2000, Windows 7, Windows NT, Windows Server 2003, Windows Server 2008, Windows Vista, Windows XP
CVE References:
The Trojan has been known the arrive on the compromised computer as a PDF file that exploits the Adobe Reader 'CoolType.dll' TTF Font Remote Code Execution Vulnerability (BID 43057).

When the Trojan is executed, it moves certain files in the %System% folder to the %Windir% folder, and modifies the files to load and execute a malicious file. Some of the targeted files are as follows:
  • %System%\winmm.dll
  • %System%\secur32.dll
  • %System%\compres.dll
  • %System%\apphelp.dll

The file name of the loaded threat may be one of the following:
  • %System%\cliconfg.ime
  • %System%\prfn0305.dat

Next, the Trojan may also create one of the following files:
  • %System%\drivers\acplec.sys
  • %System%\drivers\sp1itter.sys

It creates the following registry subkey:

Next, it creates the following registry entry:

The Trojan then connects to the following locations through http or https to receive instructions from the remote attacker:
  • lp.apanku.com
  • ad.jcrsoft.com
  • rh.jcrsoft.com
  • bot.timewalk.me
  • b0t.meibu.com

The Trojan may then perform the following actions on the compromised computer:
  • Create files
  • Inject processes with malicious payloads
  • Set up drivers and services
  • list, add, delete, and change user accounts
  • Stop the Windows firewall
  • Provide shell access on the compromised computer
  • Create and manage a proxy server with ZXSocs Proxy v1.2
  • Uninstall itself
  • Send system information to the remote attacker, including:
    • OS
    • List CD ROM, remote, fixed, and removable drives
    • Current display mode
    • Number of processors
    • System directory
    • Uptime
    • Current user
    • Host name
    • Organization
    • Owner
    • Product ID
    • Amount of RAM
    • CPU
    • Processor name

Some samples of this threat have a valid cryptographic signature, and both 32- and 64-bit samples have been seen.


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: Santiago Cortes and Nino Fred Gutierrez
Summary| Technical Details| Removal

Search Threats

Search by name
Example: W32.Beagle.AG@mm
STAR Antimalware Protection Technologies
2016 Internet Security Threat Report, Volume 21
  • Twitter
  • Facebook
  • LinkedIn
  • Google+
  • YouTube