Threat Encyclopedia

TSPY_ZBOT.YUYET

Publish date: June 23, 2014

ANALYSIS BY

Al Victor de Leon


ALIASES:

PWS:Win32/Zbot (Microsoft), Win32/Spy.Zbot.AAU trojan (Nod32), Trojan horse Zbot.JHC (AVG), Trojan-Spy.Win32.Zbot.taot (Kaspersky), Trojan.Win32.Generic!BT (Ikarus)

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: Yes

  • In the wild: Yes

OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


This ZeuS variant uses random headers and changes its file extension to make detection arduous.

To get a one-glance comprehensive view of the behavior of this Spyware, refer to the Threat Diagram shown below.

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.

It is injected into all running processes to remain memory resident.

It modifies Internet Explorer security settings. This puts the affected computer at greater risk, as it allows malicious URLs to be accessed by the computer.

It deletes itself after execution.

TECHNICAL DETAILS

File Size:

361,984 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

10 Jun 2014

Payload:

Connects to URLs/IPs, Downloads files

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 1}\{random file name 1}.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 component file(s):

  • %System%\drivers\{random file name 2}.sys - detected as RTKT_NECURS.MJYE

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

It drops the following non-malicious files:

  • %User Temp%\{random file name 3}.bat - used to delete the executed copy
  • %Application Data%\Microsoft\Address Book\{user name}.wab
  • %Application Data%\Microsoft\Address Book\{user name}.wab~
  • %Application Data%\{random file name 2}.{random extension}

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

It creates the following folders:

  • %User Temp%\{random folder 1}
  • %Application Data%\Microsoft\Address Book

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

It is injected into all running processes to remain memory resident.

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • Global\{GUID}
  • Local\{GUID}

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 1} = "%User Temp%\{random folder 1}\{random file name 1}.exe"

Other System Modifications

This spyware adds the following registry keys:

HKEY_CURRENT_USER\Software\{random key}

HKEY_CURRENT_USER\Software\Microsoft\
WAB

HKEY_CURRENT_USER\Software\Microsoft\
WAB\WAB4

HKEY_CURRENT_USER\Software\Microsoft\
WAB\WAB4\WAB File Name

It adds the following registry entries:

HKEY_CURRENT_USER\Software\{random key}
{random} = "{random}"

HKEY_CURRENT_USER\Software\Microsoft\
WAB\WAB4
OlkContactRefresh = "0"

HKEY_CURRENT_USER\Software\Microsoft\
WAB\WAB4
OlkFolderRefresh = "0"

HKEY_CURRENT_USER\Software\Microsoft\
WAB\WAB4
FirstRun = "1"

HKEY_CURRENT_USER\Software\Microsoft\
WAB\WAB4\WAB File Name
(Default) = "%Application Data%\Microsoft\Address Book\{user name}.wab"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Privacy
CleanCookies = "0"

It creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile
DisableNotifications = 1

(Note: The default value data of the said registry entry is "0".)

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\GloballyOpenPorts\
List
{random port 1}:UDP = "{random port 1}:UDP:*:Enabled:UDP {random port 1}"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\GloballyOpenPorts\
List
{random port 2}:TCP = "{random port 2}:TCP:*:Enabled:TCP {random port 2}"

Web Browser Home Page and Search Page Modification

This spyware modifies Internet Explorer zone settings.

Download Routine

This spyware connects to the following URL(s) to download its configuration file:

  • http://{random URL}

Other Details

This spyware connects to the following URL(s) to check for an Internet connection:

  • http://www.google.com

It deletes itself after execution.

NOTES:

It may also gather the following information from the affected system:

  • Data on cookie files (URLs)
  • Email-related information such as account names, email addresses, passwords, server data, and server port
  • Email information stored in the user’s Windows Address Book (WAB) file

The configuration file may contain URLs where it downloads an updated copy of itself and where it sends its gathered information. It may also contain URLs of its target online banking and finance-related sites from where it steals the information.

SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.854.03

FIRST VSAPI PATTERN DATE:

28 May 2014

VSAPI OPR PATTERN File:

10.855.00

VSAPI OPR PATTERN Date:

28 May 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

Remove grayware/spyware files dropped/downloaded by TSPY_ZBOT.YUYET

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 1} = "%User Temp%\{random folder 1}\{random file name 1}.exe"

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_CURRENT_USER\Software\Microsoft
    • WAB

Step 6

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\SharedAccess\Parameters\FirewallPolicy\StandardProfile\GloballyOpenPorts\List
    • {random port 1}:UDP = "{random port 1}:UDP:*:Enabled:UDP {random port 1}"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\GloballyOpenPorts\List
    • {random port 2}:TCP = "{random port 2}:TCP:*:Enabled:TCP {random port 2}"

Step 7

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator’s help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile
    • From: DisableNotifications = "1"
      To: DisableNotifications = "0"

Step 8

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.
  • %Application Data%\Microsoft\Address Book

Step 9

Search and delete these files

[ 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.
  • %User Temp%\{random file name 3}.bat
  • %Application Data%\{random file name 2}.{random extension}

Step 10

Reset Internet security settings

[ Learn More ]

Step 11

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TSPY_ZBOT.YUYET. 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 12

The following created files/folders/registry keys/registry entries 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 system information with a backup. Note that the said components do not have to be deleted since it won't be harmful to the system.

  • HKEY_CURRENT_USER\Software\{random key}


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