Analysis by: Francis Xavier Antazo
 PLATFORM:

Windows

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

  • 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: 348464 bytes
Memory Resident: Yes
Initial Samples Received Date: 23 Apr 2015

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 drops the following copies of itself into the affected system:

  • %Application Data%\Microsoft\(guid 1)\{random file name 1}.exe

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random file name 1} = "%Application Data%\Microsoft\(guid 1)\{random file name 1}.exe"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
{random file name 1} = "(guid 1)"

Other System Modifications

This backdoor adds the following registry entries:

HKEY_CURRENT_USER\Microsoft\Windows\
CurrentVersion
{random file name 1} = "(guid 1)"

HKEY_LOCAL_MACHINE\Microsoft\Windows\
CurrentVersion
{random file name 1} = "(guid 1)"

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}jave.myftp.org/upfornow/connect.php

  SOLUTION

Minimum Scan Engine: 9.750
FIRST VSAPI PATTERN FILE: 11.622.02
FIRST VSAPI PATTERN DATE: 06 Aug 2014
VSAPI OPR PATTERN File: 11.623.00
VSAPI OPR PATTERN Date: 06 Aug 2014

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\Microsoft\Windows\CurrentVersion
    • {random file name 1} = "(guid 1)"
  • In HKEY_CURRENT_USER\Microsoft\Windows\CurrentVersion
    • {random file name 1} = "(guid 1)"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random file name 1} = "%Application Data%\Microsoft\(guid 1)\{random file name 1}.exe"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • {random file name 1} = "%Application Data%\Microsoft\(guid 1)\{random file name 1}.exe"

Step 3

Scan your computer with your Trend Micro product to delete files detected as BKDR_ZEGOST.BNH. 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.


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