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TROJ_ZBOT.OK

October 12, 2012
 ALIASES:

PWS:Win32/Zbot.GA (Microsoft); Generic PWS.cq (McAfee); Trojan.Zbot (Symantec); Trojan-Spy.Win32.Zbot.roh (Kaspersky); Trojan.Crypt.Zcrypt (v) (Sunbelt); Application.Generic.220282 (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This Trojan 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:

303,104 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

17 Feb 2012

Arrival Details

This Trojan 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 Trojan drops the following copies of itself into the affected system:

  • %System%\ntos.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It creates the following folders:

  • %System%\wsnpoem

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Autostart Technique

This Trojan modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
userinit = "%System%\userinit.exe,%System%\ntos.exe,"

(Note: The default value data of the said registry entry is %Windows%\system32\userinit.exe,.)

Other System Modifications

This Trojan deletes the following files:

  • %System%\ntos.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It adds the following registry keys:

HKEY_CURRENT_USER\software\microsoft\
windows\currentversion\explorer\
{43BF8CD1-C5D5-2230-7BB2-98F22C2B7DC6}

HKEY_CURRENT_USER\software\microsoft\
windows\currentversion\explorer\
{35106240-D2F0-DB35-716E-127EB80A0299}

HKEY_CURRENT_USER\software\microsoft\
windows\currentversion\explorer\
{19127AD2-394B-70F5-C650-B97867BAA1F7}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Network
UID = "BRIAN-EE28CA0B0_0000B2F4"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
{43BF8CD1-C5D5-2230-7BB2-98F22C2B7DC6}
{F710FA10-2031-3106-8872-93A2B5C5C620} = "{random values}"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
{43BF8CD1-C5D5-2230-7BB2-98F22C2B7DC6}
{E716FA10-2031-AA96-8E72-93A205C5C62C} = "{random values}"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
{35106240-D2F0-DB35-716E-127EB80A0299}
{F710FA10-2031-3106-8872-93A2B5C5C620} = "{random values}"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
{35106240-D2F0-DB35-716E-127EB80A0299}
{E716FA10-2031-AA96-8E72-93A205C5C62C} = "{random values}"

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Network
UID = "BRIAN-EE28CA0B0_0000F656"

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Network
UID = "BRIAN-EE28CA0B0_00012555"

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}.83.203/zz/config.bin

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Identify and delete files detected as TROJ_ZBOT.OK using either the Startup Disk or Recovery Console

[ Learn More ]

Step 3

Delete this registry key

[ 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_CURRENT_USER\software\microsoft\windows\currentversion\explorer
    • {43BF8CD1-C5D5-2230-7BB2-98F22C2B7DC6}
  • In HKEY_CURRENT_USER\software\microsoft\windows\currentversion\explorer
    • {35106240-D2F0-DB35-716E-127EB80A0299}
  • In HKEY_CURRENT_USER\software\microsoft\windows\currentversion\explorer
    • {19127AD2-394B-70F5-C650-B97867BAA1F7}

Step 4

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\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Network
    • UID = "BRIAN-EE28CA0B0_0000B2F4"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\{43BF8CD1-C5D5-2230-7BB2-98F22C2B7DC6}
    • {F710FA10-2031-3106-8872-93A2B5C5C620} = "{random values}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\{43BF8CD1-C5D5-2230-7BB2-98F22C2B7DC6}
    • {E716FA10-2031-AA96-8E72-93A205C5C62C} = "{random values}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\{35106240-D2F0-DB35-716E-127EB80A0299}
    • {F710FA10-2031-3106-8872-93A2B5C5C620} = "{random values}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\{35106240-D2F0-DB35-716E-127EB80A0299}
    • {E716FA10-2031-AA96-8E72-93A205C5C62C} = "{random values}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Network
    • UID = "BRIAN-EE28CA0B0_0000F656"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Network
    • UID = "BRIAN-EE28CA0B0_00012555"

Step 5

Restore this modified 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\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: userinit = "%System%\userinit.exe,%System%\ntos.exe,"
      To: userinit = ""%Windows%\system32\userinit.exe,""

Step 6

Search and delete this folder

[ 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.
  • %System%\wsnpoem

Step 7

Scan your computer with your Trend Micro product to delete files detected as TROJ_ZBOT.OK. 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 8

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.

  • %System%\ntos.exe


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