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Worm:Win32/Esfury.X


Worm:Win32/Esfury.X is a worm - a self-propagating program that can spread itself from one computer to another. Worms may spread themselves via a variety of different channels in order to compromise new computers. Commonly, worms may spread directly by copying themselves to removable or network drives, or by attempting to exploit particular vulnerabilities on targeted computers. Worms also often attempt to spread via platforms that require user interaction in order to run. They may send themselves as an attachment to an email or an instant message, or send a link to a copy of themselves in the body of a message. In these cases the message needs to be convincing enough to encourage the victim to click on the link or attachment and run or download a copy of the worm.


What to do now

To detect and remove this threat and other malicious software that may have been installed in your computer, run a full-system scan with an up-to-date antivirus product such as the following: For more information about using antivirus software, see http://www.microsoft.com/windows/antivirus-partners/.

Additional remediation instructions

This threat may make lasting changes to an affected system's configuration that will NOT be restored by detecting and removing this threat. For more information on returning an affected system to its pre-infected state, please see the following information:
Disable Autorun functionality
Worm:Win32/Esfury.X attempts to spread via removable drives on computers that support Autorun functionality. This is a particularly common method of spreading for many current malware families. For information on disabling Autorun functionality, please see the following article: http://support.microsoft.com/kb/967715/
To recreate a clean Hosts file:
See How do I reset the Hosts file back to the default?

Threat behavior

Worm:Win32/Esfury.X is a worm - a self-propagating program that can spread itself from one computer to another. Worms may spread themselves via a variety of different channels in order to compromise new computers. Commonly, worms may spread directly by copying themselves to removable or network drives, or by attempting to exploit particular vulnerabilities on targeted computers. Worms also often attempt to spread via platforms that require user interaction in order to run. They may send themselves as an attachment to an email or an instant message, or send a link to a copy of themselves in the body of a message. In these cases the message needs to be convincing enough to encourage the victim to click on the link or attachment and run or download a copy of the worm.
Installation
Worm:Win32/Esfury.X creates the following files on an affected computer:

  • %windir%\windowsupdate.log
Spreads via…
Removable drives
Worm:Win32/Esfury.X may create the following files on targeted drives when spreading:

  • <targeted drive>:\subst .lnk
  • <targeted drive>:\125cfaffc54d6d4c49e4\desktop.ini
  • <targeted drive>:\125cfaffc54d6d4c49e4\s-1-3-01-4631041401-305419896-464015834-1505\desktop.ini

It also places an autorun.inf file in the root directory of the targeted drive. Such autorun.inf files contain execution instructions for the operating system, so that when the removable drive is accessed from another computer supporting the Autorun feature, the malware is launched automatically.

Note: This worm was observed to write an executable and create an autorun.inf file on a targeted drive in our automated testing environment. This is particularly common malware behavior, generally utilized in order to spread malware from computer to computer.
It should also be noted that autorun.inf files on their own are not necessarily a sign of infection, as they are used by legitimate programs and installation CDs.
Payload
Modifies Hosts file
Worm:Win32/Esfury.X modifies the Windows Hosts file. The local Hosts file overrides the DNS resolution of a website URL to a particular IP address. Malicious software may make modifications to the Hosts file in order to redirect specified URLs to different IP addresses. Malware often modifies an affected computer's Hosts file in order to stop users from accessing websites associated with particular security-related applications (such as antivirus for example).

Terminates processes
The malware terminates the following processes should they be running on an affected computer:

  • _avpm.exe
  • antivirus.exe
  • AUPDATE.EXE
  • AVGW.EXE
  • avp32.exe
  • avpcc.exe
  • blackice.exe
  • cmd.exe
  • DRWEB32.EXE
  • egui.exe
  • ekrn.exe
  • fsav.exe
  • NAVW32.exe
  • NOD32.EXE
  • PERSFW.EXE
  • rav.exe
  • SCAN32.exe
  • wuauclt.exe
  • ZONEALARM.EXE

Contacts remote hosts
The malware may contact the following remote hosts using port 80:

  • whos.amung.us
  • www.buscaid.com

Commonly, malware may contact a remote host for the following purposes:
  • To confirm Internet connectivity
  • To report a new infection to its author
  • To receive configuration or other data
  • To download and execute arbitrary files (including updates or additional malware)
  • To receive instruction from a remote attacker
  • To upload data taken from the affected computer

This malware description was produced and published using our automated analysis system's examination of file SHA1 08d805c727ac4fd895a26d3b6f7aab98ebbad0aa.

Symptoms

System changes
The following system changes may indicate the presence of this malware:

  • The presence of the following files:

  • %windir%\windowsupdate.log


Prevention


Alert level: Severe
First detected by definition: 1.135.81.0
Latest detected by definition: 1.183.1052.0 and higher
First detected on: Aug 29, 2012
This entry was first published on: Sep 06, 2012
This entry was updated on: Sep 17, 2012

This threat is also detected as:
No known aliases