Analysis by: Jaime Benigno Reyes
ALIASES:

Worm:Win32/Rebhip.A (Microsoft), Worm.Win32.Luder.tvz (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:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware, Propagates via flashdrives

This malware was involved in an attack targeting Banco de Brasil users during May 2013. It came bundled as a plugin for a customized banking browser. Once executed, it steals banking information from the affected system. Users with systems affected by this malware may find their online banking accounts compromised.

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

This worm arrives by connecting affected removable drives to a system. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

  TECHNICAL DETAILS

File Size: 323,912 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 06 May 2013
Payload: Drops files, Steals information

Arrival Details

This worm arrives by connecting affected removable drives to a system.

It 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 worm drops the following copies of itself into the affected system and executes them:

  • %System%\install\server.exe

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

It drops the following component file(s):

  • %Application Data%\logs.dat
  • %User Temp%\XX--XX--XX.TXT
  • %User Temp%\UuU.uUu
  • %User Temp%\XxX.xXx

(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.. %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 creates the following folders:

  • %System%\install

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

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

  • _x_X_UPDATE_X_x_
  • _x_X_PASSWORDLIST_X_x_
  • _x_X_BLOCKMOUSE_X_x_
  • ***MUTEX***
  • ***MUTEX***_PERSIST

It stays memory-resident by injecting codes into the following processes:

  • explorer.exe
  • iexplore.exe

Autostart Technique

This worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
Policies = "%System%\install\server.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
Policies = "%System%\install\server.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HKLM = "%System%\install\server.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
HKCU = "%System%\install\server.exe"

Other System Modifications

This worm adds the following registry keys:

HKEY_CURRENT_USER\Software\vítima

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{08B0E5JF-4FCB-11CF-AAA5-00401C6XX500}

It adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\vítima
FirstExecution = "{current date and time with this format: dd/mm/yyy -- hh:mm}"

HKEY_CURRENT_USER\Software\vítima
NewIdentification = "vítima"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{08B0E5JF-4FCB-11CF-AAA5-00401C6XX500}
StubPath = "%System%\install\server.exe"

Propagation

This worm creates the following folders in all removable drives:

  • {removable drive letter}:\RECYCLER
  • {removable drive letter}:\RECYCLER\S-1-5-21-1482476501-3352491937-682996330-1013

It drops the following copy(ies) of itself in all removable drives:

  • {removable drive letter}:\RECYCLER\S-1-5-21-1482476501-3352491937-682996330-1013\server.exe

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[autorun]
;open=RECYCLER\S-1-5-21-1482476501-3352491937-682996330-1013\server.exe
icon=shell32.dll,4
shellexecute=RECYCLER\S-1-5-21-1482476501-3352491937-682996330-1013\server.exe
label=PENDRIVE
action=Open folder to view files
shell\Open=Open
shell\Open\command=RECYCLER\S-1-5-21-1482476501-3352491937-682996330-1013\server.exe
shell\Open\Default=1

Information Theft

This worm gathers the following data:

  • sensitive information such as account names, email addresses and passwords by monitoring web activities and logging keystrokes

Stolen Information

This worm sends the gathered information via HTTP POST to the following URL:

  • {BLOCKED}-200-41.{BLOCKED}ol.com.br

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.900.05
FIRST VSAPI PATTERN DATE: 06 May 2013
VSAPI OPR PATTERN File: 9.901.00
VSAPI OPR PATTERN Date: 07 May 2013

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

Restart in Safe Mode

[ Learn More ]

Step 3

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\CurrentVersion\policies\Explorer\Run
    • Policies = "%System%\install\server.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
    • Policies = "%System%\install\server.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HKLM = "%System%\install\server.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HKCU = "%System%\install\server.exe"

Step 4

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
    • vítima
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {08B0E5JF-4FCB-11CF-AAA5-00401C6XX500}

Step 5

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%\logs.dat
  • %User Temp%\XX--XX--XX.TXT
  • %User Temp%\UuU.uUu
  • %User Temp%\XxX.xXx

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.
  • %System%\install
  • {removable drive letter}:\RECYCLER

Step 7

Search and delete AUTORUN.INF files created by WORM_LUDER.USR that contain these strings

[ Learn More ]
[autorun]
;open=RECYCLER\S-1-5-21-1482476501-3352491937-682996330-1013\server.exe
icon=shell32.dll,4
shellexecute=RECYCLER\S-1-5-21-1482476501-3352491937-682996330-1013\server.exe
label=PENDRIVE
action=Open folder to view files
shell\Open=Open
shell\Open\command=RECYCLER\S-1-5-21-1482476501-3352491937-682996330-1013\server.exe
shell\Open\Default=1

Step 8

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