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BKDR_ZEGOST.OC

November 16, 2013
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size:

109,279 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

16 Nov 2013

Arrival Details

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This backdoor creates the following folders:

  • %User Profile%\CryptnetUrlCache\MetaData
  • %User Profile%\Microsoft\CryptnetUrlCache
  • %User Profile%\CryptnetUrlCache\Content

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

Other System Modifications

This backdoor deletes the following files:

  • %User Temp%\nsl1.tmp

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Defghi Klmnopqr Tuv
Description = "Defghijk Mnopqrstu Wxyabcd Fghijklm Opq"

Dropping Routine

This backdoor drops the following files:

  • \Install.exe
  • \ReadyFor4GB.exe
  • %User Profile%\MetaData\3C83474D61E624A4F9844DF935AFE217
  • %User Profile%\Content\3C83474D61E624A4F9844DF935AFE217
  • %User Profile%\MetaData\303572DF538EDD8B1D606185F1D559B8
  • %User Profile%\Content\303572DF538EDD8B1D606185F1D559B8
  • %User Profile%\MetaData\79841F8EF00FBA86D33CC5A47696F165
  • %User Profile%\Content\79841F8EF00FBA86D33CC5A47696F165
  • %User Temp%\svchest.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Defghi Klmnopqr Tuv
    • Description = "Defghijk Mnopqrstu Wxyabcd Fghijklm Opq"

Step 3

Search and delete these components

[ Learn More ]
There may be some components that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • \Install.exe
  • \ReadyFor4GB.exe
  • %User Profile%\MetaData\3C83474D61E624A4F9844DF935AFE217
  • %User Profile%\Content\3C83474D61E624A4F9844DF935AFE217
  • %User Profile%\MetaData\303572DF538EDD8B1D606185F1D559B8
  • %User Profile%\Content\303572DF538EDD8B1D606185F1D559B8
  • %User Profile%\MetaData\79841F8EF00FBA86D33CC5A47696F165
  • %User Profile%\Content\79841F8EF00FBA86D33CC5A47696F165
  • %User Temp%\svchest.exe

Step 4

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Profile%\CryptnetUrlCache\MetaData
  • %User Profile%\Microsoft\CryptnetUrlCache
  • %User Profile%\CryptnetUrlCache\Content

Step 5

Scan your computer with your Trend Micro product to delete files detected as BKDR_ZEGOST.OC. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.

Step 6

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %User Temp%\nsl1.tmp


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