TSPY_ZBOT.YUYADW

 Analysis by: David John Agni

 ALIASES:

Infostealer.Limitail (Symantec), PWS:Win32/Zbot (Microsoft)

 PLATFORM:

Windows

 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.

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.

  TECHNICAL DETAILS

File Size:

217,600 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

25 Jun 2015

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:

  • %Application Data%\{random folder 1}\{random file name 1}.exe
  • %Application Data%\{random folder 3}\{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.)

It drops the following files:

  • %Application Data%\{random folder 2}\{random filename 2}.tmp
  • %Application Data%\{random folder 2}\{random filename 2}.{random extension}
  • %User Temp%\tmp{random}.bat
  • %Application Data%\Sample.lnk

(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.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)

It creates the following folders:

  • %Application Data%\{random folder 1}
  • %Application Data%\{random folder 2}
  • %Application Data%\{random folder 3}

(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 spyware adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
sidebar = "%Application Data%\Sample.lnk"

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

Other System Modifications

This spyware adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
{random key}

It adds the following registry entries:

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\
{random key}
{random} = "{hex values}"

Web Browser Home Page and Search Page Modification

This spyware modifies Internet Explorer zone settings.

Other Details

This spyware connects to the following possibly malicious URL:

  • http://{BLOCKED}te.com/download/logs/kng/45/config.bin

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.726.03

FIRST VSAPI PATTERN DATE:

12 Jun 2015

VSAPI OPR PATTERN File:

11.727.00

VSAPI OPR PATTERN Date:

13 Jun 2015

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

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
    • {GUID} = "%Application Data%\{random folder 1}\{random file name 1}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • sidebar = "%Application Data%\Sample.lnk"

Step 5

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 folder 1}
  • %Application Data%\{random folder 2}
  • %Application Data%\{random folder 3}

Step 6

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.
  • %Application Data%\Sample.lnk
  • %User Temp%\\tmp{random}.bat

Step 7

Reset Internet security settings

[ Learn More ]

Step 8

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