1. Symantec/
  2. Security Response/
  3. W32.Eternalrocks

W32.Eternalrocks

Risk Level 1: Very Low

Discovered:
May 21, 2017
Updated:
May 24, 2017 2:17:58 PM
Type:
Trojan, Worm
Infection Length:
Varies
Systems Affected:
Windows
The worm spreads by exploiting critical Server Message Block (SMB) remote code execution (RCE) vulnerabilities in Windows computers, which were patched by Microsoft in March 2017 (MS17-010).

When the worm is executed, it creates the following folders:
  • %ProgramFiles%\Microsoft Updates\SharpZLib
  • %ProgramFiles%\Microsoft Updates\Temp\Data\Tor\geoip
  • %ProgramFiles%\Microsoft Updates\Temp\Data\Tor\geoip6
  • %ProgramFiles%\Microsoft Updates\Tor\lock
  • %ProgramFiles%\Microsoft Updates\Tor\torrc
  • %ProgramFiles%\Microsoft Updates\Tor\state
  • %ProgramFiles%\Microsoft Updates\Tor\hidden_service\hostname
  • %ProgramFiles%\Microsoft Updates\Tor\hidden_service\private_key

The worm also creates the following files:
  • %ProgramFiles%\Microsoft Updates\installed.fgh
  • %ProgramFiles%\Microsoft Updates\SharpZLib.zip
  • %ProgramFiles%\Microsoft Updates\ICSharpCode.SharpZipLib.dll
  • %ProgramFiles%\Microsoft Updates\Microsoft.Win32.TaskScheduler.dll
  • %ProgramFiles%\Microsoft Updates\svchost.exe
  • %ProgramFiles%\Microsoft Updates\taskhost.exe
  • %ProgramFiles%\Microsoft Updates\torunzip.exe
  • %ProgramFiles%\Microsoft Updates\Temp\tor.zip
  • %ProgramFiles%\Microsoft Updates\Tor\libeay32.dll
  • %ProgramFiles%\Microsoft Updates\Tor\libevent-2-0-5.dll
  • %ProgramFiles%\Microsoft Updates\Tor\libevent_core-2-0-5.dll
  • %ProgramFiles%\Microsoft Updates\Tor\libevent_extra-2-0-5.dll
  • %ProgramFiles%\Microsoft Updates\Tor\libgcc_s_sjlj-1.dll
  • %ProgramFiles%\Microsoft Updates\Tor\libssp-0.dll
  • %ProgramFiles%\Microsoft Updates\Tor\ssleay32.dll
  • %ProgramFiles%\Microsoft Updates\Tor\tor.exe
  • %ProgramFiles%\Microsoft Updates\Tor\zlib1.dll
  • %ProgramFiles%\Microsoft Updates\required.glo

The worm then creates the following mutexes so that only one instance of the threat executes on the computer:
  • {8F6F00C4-B901-45fd-08CF-72FDEFF}
  • {8F6F0AC4-B9A1-45fd-A8CF-72FDEFF}
  • 20b70e57-1c2e-4de9-99e5-69f369006912

The worm connects to the following remote location to check for updates:
  • http://ubgdgno5eswkhmpy.onion/updates/info?id=%computername%&v=1.1.27&download=next

If updates are available, the worm downloads them from the following remote location:
  • http://ubgdgno5eswkhmpy.onion/updates/download?id=%computername%

The worm then saves the updates to the following location:
  • %ProgramFiles%\Microsoft Updates\taskhost.exe

Next, the worm downloads the Tor browser from the following remote location:
  • https://archive.torproject.org/tor-package-archive/torbrowser/4.0.1/tor-win32-tor-0.2.5.10.zip

The worm then saves it to the following location:
  • %ProgramFiles%\Microsoft Updates\tor.zip

Next, the worm creates the following scheduled tasks:
  • Microsoft Service Host
  • Microsoft Task Host
  • Microsoft Tor Host

The worm creates firewall rules for following files to allow communication:
  • %ProgramFiles%\Microsoft Updates\svchost.exe
  • %ProgramFiles%\Microsoft Updates\taskhost.exe
  • %ProgramFiles%\Microsoft Updates\Tor\tor.exe

The worm creates a firewall rule to block inbound connections to port 445.

Next, the worm installs the following threat on the compromised computer:

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: Yusuke Kudo, Jeet Morparia
Summary| Technical Details| Removal

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