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TROJ_FAKEAV.LEXA

October 08, 2012
 Analysis by: Erika Bianca Mendoza
 ALIASES:

TR/FakeAV.bhaw (Antivir)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild:

  OVERVIEW


This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It installs a fake antivirus/antispyware software. It displays fake alerts that warn users of infection. It also displays fake scanning results of the affected system. It then asks for users to purchase it once scanning is completed. If users decide to purchase the rogue product, users are directed to a certain website asking for sensitive information, such as credit card numbers.

  TECHNICAL DETAILS

File Size:

858624 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

25 Mar 2011

Payload:

Connects to URLs/Ips

Arrival Details

This Trojan 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 Trojan drops the following files:

  • %System%\us?rinit.exe
  • %User Temp%\{E9C1E0AC-C9B1-4c85-94DE-9C1518918D01}.tlb
  • %User Temp%\{E9C1E0AC-C9B1-4c85-94DE-9C1518918D02}.tlb
  • %system%\exefile.exe
  • %system%\drivers\vbma{random}.sys
  • %system%\ms{randomchars}.dll

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.. %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.)

Autostart Technique

This Trojan registers its dropped component as a system service to ensure its automatic execution at every system startup. It does this by creating the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\userinit
Start = 2

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\userinit
Type = 10

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\userinit
ErrorControl = 0

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\userinit
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\userinit
DisplayName = "Antivirus 2010"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\userinit
Description = "AV software"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\userinit
ImagePath = "\.\globalroot\systemroot\system32\us?rinit.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
{7F230CA0-D973-ECA8-E4E4-E28DBBEC2277}

HKEY_LOCAL_MACHINE\Interface\{66b993fe-420b-8977-5143-d1c92318606e}

HKEY_LOCAL_MACHINE\Interface\{cbe93010-4b77-9e68-7952-c6c546e1b0c4}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
{7F230CA0-D973-ECA8-E4E4-E28DBBEC2277}
DisplayIcon = "\.\globalroot\systemroot\system32\us?rinit.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
{7F230CA0-D973-ECA8-E4E4-E28DBBEC2277}
NoModify = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
{7F230CA0-D973-ECA8-E4E4-E28DBBEC2277}
URLInfoAbout = http://www.webtopbilling.com/

HKEY_CLASSES_ROOT\Interface\{cbe93010-4b77-9e68-7952-c6c546e1b0c4}
u = "131253"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
{7F230CA0-D973-ECA8-E4E4-E28DBBEC2277}
NoRepair = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
{7F230CA0-D973-ECA8-E4E4-E28DBBEC2277}
u = 200b5

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
{7F230CA0-D973-ECA8-E4E4-E28DBBEC2277}
t = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
{7F230CA0-D973-ECA8-E4E4-E28DBBEC2277}
a = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
{7F230CA0-D973-ECA8-E4E4-E28DBBEC2277}
DisplayName = "Antivirus 2010"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
{7F230CA0-D973-ECA8-E4E4-E28DBBEC2277}
Publisher = "WebTop Software Limited"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
{7F230CA0-D973-ECA8-E4E4-E28DBBEC2277}
UninstallString = "\.\globalroot\systemroot\system32\us?rinit.exe /uninstall"

It modifies the following registry entries:

HKEY_CLASSES_ROOT\exefile\shell\
open\command
(Default) = ""exefile" /shell <%1> %*"

(Note: The default value data of the said registry entry is ""%1" %*".)

Dropping Routine

This Trojan drops the following files:

  • %System%\exefile.exe - detected as TROJ_FAKEAV.LEXB

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.226.180:8083/ask?t=1&u=131253&a=0&m=11f430bb&h=a269ce8d
  • http://{BLOCKED}.{BLOCKED}.226.180:8083/ask?t=1&u=131253&a=21&m=11f430bb&h=a269ce8d
  • http://{BLOCKED}.{BLOCKED}.226.180:8083/ask?t=1&u=131253&a=31&m=11f430bb&h=a269ce8d
  • http://{BLOCKED}.{BLOCKED}.226.180:8083/ask?t=1&u=131253&a=44&m=11f430bb&h=a269ce8d

Rogue Antivirus Routine

This Trojan installs a fake antivirus/antispyware software.

It displays fake alerts that warn users of infection. It also displays fake scanning results of the affected system. It then asks for users to purchase it once scanning is completed. If users decide to purchase the rogue product, users are directed to a certain website asking for sensitive information, such as credit card numbers.