Analysis by: Rika Joi Gregorio
ALIASES:

Worm:Win32/Rebhip.A(Microsoft), Virus.Win32.VBInject(Ikarus), a variant of Win32/Injector.AZJ trojan(Eset)

 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:

  • In the wild: Yes

  OVERVIEW

This worm 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: 339,968 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 04 May 2013

Arrival Details

This worm 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 files:

  • %Application Data%\logs.dat
  • %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.)

Autostart Technique

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

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

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

HKEY_LOCAL_MACHINE\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"

Other System Modifications

This worm adds the following registry keys:

HKEY_CURRENT_USER\Software\Victim

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{random}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Victim
FirstExecution = "{Date of 1st execution} -- {Time of 1st execution}"

HKEY_CURRENT_USER\Software\Victim
NewIdentification = "Victim"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{random}
StubPath = "%System%\install\server.exe"

Propagation

This worm creates the following folders in all removable drives:

  • {Drive Letter}:\RECYCLER
  • {Drive Letter}:\RECYCLER\S-1-5-21-{random}

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

  • {Drive Letter}:\RECYCLER\S-1-5-21-{random}\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-{random}\server.exe
icon=shell32.dll,4
shellexecute=RECYCLER\S-1-5-21-{random}\server.exe
label=PENDRIVE
action=Open folder to view files
shell\Open=Open
shell\Open\command=RECYCLER\S-1-5-21-{random}\server.exe
shell\Open\Default=1