TSPY_ZBOT.YUYEL

 Analysis by: Jaime Benigno Reyes

 ALIASES:

Trojan-Spy.Win32.Zbot.tbuo (Kaspersky)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Spyware

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This spyware 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:

592,896 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

04 Jun 2014

Arrival Details

This spyware 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 spyware drops the following copies of itself into the affected system and executes them:

  • %User Temp%\{random folder}\{random file name}.exe

(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 drops the following files:

  • %System%\drivers\{16 alphanumeric characters}.sys

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It creates the following folders:

  • %User Temp%\{random folder}

(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.)

Autostart Technique

This spyware 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} = "%User Temp%\{random folder}\{random file name}.exe"

Other System Modifications

This spyware adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{16 alphanumeric characters}

HKEY_CURRENT_USER\Software\{random}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{16 alphanumeric characters}
ImagePath = "\SystemRoot\System32\Drivers\{16 alphanumeric characters}.sys"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{16 alphanumeric characters}
Group = "Boot Bus Extender"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{16 alphanumeric characters}
ErrorControl = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{16 alphanumeric characters}
Type = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{16 alphanumeric characters}
Start = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{16 alphanumeric characters}
Tag = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{16 alphanumeric characters}
DisplayName = "{malware file name}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{16 alphanumeric characters}
DB6 = {hex value}

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{16 alphanumeric characters}
DB5 = {hex value}

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\GloballyOpenPorts\
List
{random port}:TCP = "{random port}:TCP:*:Enabled:TCP {random port}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\GloballyOpenPorts\
List
{random port}:UDP = "{random port}:UDP:*:Enabled:UDP {random port}"

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.838.01

FIRST VSAPI PATTERN DATE:

04 Jun 2014

VSAPI OPR PATTERN File:

10.839.00

VSAPI OPR PATTERN Date:

04 Jun 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

Scan your computer with your Trend Micro product and note files detected as TSPY_ZBOT.YUYEL

Step 3

Restart in Safe Mode

[ Learn More ]

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random file name} = "%User Temp%\{random folder}\{random file name}.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\GloballyOpenPorts\List
    • {random port}:TCP = "{random port}:TCP:*:Enabled:TCP {random port}"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\GloballyOpenPorts\List
    • {random port}:UDP = "{random port}:UDP:*:Enabled:UDP {random port}"

Step 5

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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • {16 alphanumeric characters}
  • In HKEY_CURRENT_USER\Software
    • {random}

Step 6

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 Temp%\{random folder}

Step 7

Search and delete this file

[ Learn More ]
There may be some files 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.
  • %System%\drivers\{16 alphanumeric characters}.sys

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TSPY_ZBOT.YUYEL. 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 9

The following created registry key(s) cannot be identified by the user since there are no reference values in the created key. The only way it can be identified is by comparing the present keys with a backup of the system registry. Note that the said key(s) do not have to be deleted since it won't be harmful to the system:

  • HKEY_CURRENT_USER\Software\{random}


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