Threat Encyclopedia

TSPY_ZBOT.UYG

Publish date: March 17, 2013

ANALYSIS BY

Michael Cabel


ALIASES:

PWS:Win32/Zbot. (Microsoft)

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:
REPORTED INFECTION:
SYSTEM IMPACT RATING:
INFORMATION EXPOSURE:

  • Threat Type:Spyware

  • Destructiveness:No

  • Encrypted: No

  • In the wild: Yes

OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


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 may be downloaded by other malware/grayware from remote sites.

It does not have any propagation routine.

It does not have any backdoor routine.

It modifies the Internet Explorer Zone Settings.

As of this writing, the said sites are inaccessible.

TECHNICAL DETAILS

File Size:

313,344 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

14 Mar 2013

Payload:

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.

It may be downloaded by the following malware/grayware from remote sites:

  • TSPY_TEPFER.UYG

Installation

This spyware drops the following files:

  • %Application Data%\{random letters 1}\{random letters}.exe - copy of itself
  • %Application Data%\{random letters 2}\{random letters}.{random letters} - encrypted file

(Note: %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:

  • %Application Data%\{random letters 1}
  • %Application Data%\{random letters 2}

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

  • Global\{random GUID}
  • Local\{random GUID}

It injects itself into the following processes as part of its memory residency routine:

  • explorer.exe

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 Characters} = "%Application Data%\{random letters 1}\{random letters}.exe"

Other System Modifications

This spyware adds the following registry keys as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
{random letters}

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile\AuthorizedApplications\
List
%Windows%\explorer.exe = "%Windows%\explorer.exe"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%Windows%\explorer.exe = "%Windows%\explorer.exe"

Propagation

This spyware does not have any propagation routine.

Backdoor Routine

This spyware does not have any backdoor routine.

Web Browser Home Page and Search Page Modification

This spyware modifies the Internet Explorer Zone Settings.

Download Routine

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

  • {BLOCKED}.{BLOCKED}.127.98
  • {BLOCKED}.{BLOCKED}.145.32
  • {BLOCKED}.{BLOCKED}.161.171
  • {BLOCKED}.{BLOCKED}.25.54

As of this writing, the said sites are inaccessible.

NOTES:

It saves a copy of the Windows Address Book as the following:

  • %User Profile%\Application Data\Microsoft\Address Book\{User Name}.wab
  • %User Profile%\Application Data\Microsoft\Address Book\{User Name}.wab~

It may access a remote site to download its configuration file. It may monitor several finance-related institutions depending on the contents of the configuration file.

The configuration file also contains the drop zone where it sends stolen information, the URL where the configuration file can be downloaded, the codes for web injection, and the monitored URLs. However, it fails to download its configuration file because it is already inaccessible.

SOLUTION

Minimum Scan Engine:

9.200

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 malware/grayware files that dropped/downloaded TSPY_ZBOT.UYG

    TSPY_TEPFER.UYG

Step 3

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

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

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 Characters} = "%User Profile%\Application Data\{random folder name 1}\{random file name 1}.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
    • %Windows%\explorer.exe = "%Windows%\explorer.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %Windows%\explorer.exe = "%Windows%\explorer.exe"

Step 6

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CURRENT_USER\Software\Microsoft
    • {random letters}

Step 7

Reset Internet security settings

[ Learn More ]

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%\{random letters 1}
  • %Application Data%\{random letters 2}

Step 9

Search and delete these files

[ Learn More ]
There may be some component 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 Profile%\Application Data\Microsoft\Address Book\{User Name}.wab
  • %User Profile%\Application Data\Microsoft\Address Book\{User Name}.wab~

Step 10

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TSPY_ZBOT.UYG. 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 11

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\Microsoft\{random letters}

Step 12

Scan your computer with your Trend Micro product to delete files detected as TSPY_ZBOT.UYG. 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.

NOTES:

The created registry key HKEY_CURRENT_USER\Software\Microsoft\{random letters} cannot be identified by the users 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 if the users have one. Note that the key, {random letters} need not to be deleted since it won't cause the user system any harm. In deleting the created folders, please take note of the malware path of the file(s) detected earlier.


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