Worm:Win32/Esfury.O

Detected by Microsoft Defender Antivirus

Aliases: Worm.Win32.Esfury (Ikarus) Trojan.Win32.VBKrypt.gbx (Kaspersky) Downloader-CJX.gen.j (McAfee) W32/VBKrypt.AA (Norman) Mal/SillyFDC-G (Sophos) WORM_ESFURY.SMM (Trend Micro)

Summary

Worm:Win32/Esfury.O is a worm that spreads to all removable and network drives and connects to certain websites. The worm terminates and redirects certain processes and makes changes to the local "Hosts" file and Internet Explorer's start page. The worm changes other system settings that may lower the overall security of the computer.

To detect and remove this threat and other malicious software that may be installed in your computer, run a full-system scan with an up-to-date antivirus product such as the following:

Microsoft Security Essentials

Microsoft Safety Scanner

For more information on antivirus software, see http://www.microsoft.com/windows/antivirus-partners/.

Recovering from recurring infections on a network

The following additional steps may need to be taken to completely remove this threat from an infected network, and to stop infections from recurring from this and other similar types of network-spreading malware:

Ensure that an antivirus product is installed on ALL computers connected to the network that can access or host shares.
Ensure that all available network shares are scanned with an up-to-date antivirus product.
Restrict permissions as appropriate for network shares on your network. For more information on simple access control, please see: http://technet.microsoft.com/library/bb456977.aspx.
Remove any unnecessary network shares or mapped drives.

Note: Additionally it may be necessary to temporarily change the permission on network shares to read-only until the disinfection process is complete.

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:

Recreate a clean Hosts file: