1. Symantec/
  2. Security Response/
  3. W32.Waledac.C


Risk Level 1: Very Low

February 8, 2012
April 17, 2013 1:56:07 PM
Also Known As:
Troj/Agent-ABGQ [Sophos], Troj/Tepfer-Q [Sophos], Troj/Backdr-IN [Sophos]
Infection Length:
883,200 bytes
Systems Affected:
When the worm executes, it checks for the presence of the following shared memory object:

If the above shared memory object exists, the worm ends the process that owns it and then creates a new one with the same name. The worm does this so that only one instance of the threat is running on the compromised computer.

Next, the worm drops the following files:
  • %System%\Packet.dll
  • %System%\drivers\npf.sys
  • %System%\wpcap.dll

It then creates the following registry entry so that it executes whenever Windows starts:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\"MozillaAgent" = "%CurrentFolder%\[ORIGINAL THREAT FILE NAME].exe"

The worm also creates the following registry entries:
  • HKEY_CURRENT_USER\Software\Mozilla\"ID" = "[RANDOM NUMBER]"
  • HKEY_CURRENT_USER\Software\Mozilla\"ID2" = "[BINARY DATA]"
  • HKEY_CURRENT_USER\Software\Mozilla\"ID3" = "[BINARY DATA]"

Next, the worm creates a service with the following characteristics:
Display Name: WinPcap Packet Driver (NPF)
Image Path: system32\drivers\NPF.sys
Startup Type: Manual

It then creates the following registry subkey in order to register the above service:

Next, the worm opens a back door on TCP port 80 and awaits further instructions from a remote attacker, which may include:
  • Download and execute files
  • Send email
  • Steal information from the compromised computer

The worm then searches for email addresses on local drives by searching all files that do not have the following extensions:
  • .7z
  • .avi
  • .bmp
  • .class
  • .dll
  • .exe
  • .gif
  • .gz
  • .hxd
  • .hxh
  • .hxn
  • .hxw
  • .jar
  • .jpeg
  • .jpg
  • .mov
  • .mp3
  • .msi
  • .ocx
  • .ogg
  • .png
  • .rar
  • .vob
  • .wav
  • .wave
  • .wma
  • .wmv
  • .zip

It then sends an email message to the collected email addresses.

The threat may also spread by copying itself to removable drives as the following file:

It may also create a link to itself on the removable drive as the following file:
%DriveLetter%\Shortcut to Sony.lnk

The worm may then attempt to steal sensitive information from network traffic, including:
  • FTP user name
  • FTP password


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: Liang Yuan
Summary| Technical Details| Removal

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