Analysis by: Francis Xavier Antazo
ALIASES:

Trojan.Cozer (Symantec)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

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

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

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size: 1,192,744 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 28 Jan 2015
Payload: Connects to URLs/IPs, Compromises system security, Drops files

Arrival Details

This backdoor 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 backdoor drops the following component file(s):

  • %Application Data%\ATI_Subsystem\atiadlxx.dll (will be detected as BKDR64_COZER.AA)
  • %Application Data%\ATI_Subsystem\aticfx32.bin
  • %Application Data%\ATI_Subsystem\aticfx32.dll (will be detected as BKDR_COZER.AA)
  • %Application Data%\ATI_Subsystem\coinst_13.152.dll (will be detected as BKDR_COZER.AA)
  • %Application Data%\ATI_Subsystem\racss.dat

(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 and executes the following files:

  • %User Temp%\reader_sl.exe (will be detected as BKDR_COZER.AA)

(Note: %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 drops the following non-malicious file:

  • %Application Data%\ATI_Subsystem\clinfo.exe (copy of rundll32.exe)
  • %User Temp%\hppscan854.pdf

(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.)

Other System Modifications

This backdoor deletes the following files:

  • %User Temp%\reader_sl.exe

(Note: %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 adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
ativvaxy_cik_API = ""%Application Data%\ATI_Subsystem\clinfo.exe""%Application Data%\ATI_Subsystem\aticfx32.dll", ADL_Display_DeviceConfig_Get"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
clinfo_x64 = ""%Application Data%\ATI_Subsystem\clinfo.exe""%Application Data%\ATI_Subsystem\aticfx32.dll", ADL_Display_DeviceConfig_Get"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
atipblag_x64 = ""%Application Data%\ATI_Subsystem\clinfo.exe""%Application Data%\ATI_Subsystem\aticfx32.dll", ADL_Display_DeviceConfig_Get"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Download arbitrary files
  • Upload arbitrary files
  • Execute arbitrary files
  • End arbitrary processes
  • Collect system information such as user name, computer name, operating system version, IP address, MAC address, security software installed

It connects to the following websites to send and receive information:

  • 200.119.128.45:443
  • 202.206.232.20:443

NOTES:

It drops the following .JOB file to execute the dropped component file

  • %Windows%\Tasks\atioglxx_Ext.job

    It uses the icon of a .PDF file in order to disguise it as such.

    It then opens its dropped .PDF file to trick the user that a .PDF file has indeed been opened.

    It terminates itself if it finds any of these running processes

    • APISPY32.EXE
    • APIMONITOR.EXE
    • WINAPIOVERIDE32.EXE
    • PROCEXP.EXE
    • PROCMON.EXE
    • FILEMON.EXE
    • REGMON.EXE
    • WINSPY.EXE
    • WIRESHARK.EXE
    • DUMPCAP.EXE
    • TCPDUMP.EXE
    • TCPVIEW.EXE
    • WINDUMP.EXE
    • NETSNIFFER.EXE
    • IRIS.EXE
    • COMMVIEW.EXE
    • OLLYDBG.EXE
    • SYSER.EXE
    • IDAG.EXE
    • IDAG64.EXE
    • PETOOLS.EXE
    • IDAQ.EXE
    • IDAQ64.EXE

    It searches for the following installed antivirus products:

    • Comodo Dragon
    • KASPERSKY
    • AVIRA
    • Panda
    • AVG
    • Computer Sceurity
    • SOPHOS
    • Dr.Web
    • Crystal

    It also searches for the following virtual environments:

    • VMWare
    • SANDBOX

    It also tries to find the firewall installed in the system.

    •   SOLUTION

    Minimum Scan Engine: 9.750

    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_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
      • ativvaxy_cik_API = ""%Application Data%\ATI_Subsystem\clinfo.exe""%Application Data%\ATI_Subsystem\aticfx32.dll", ADL_Display_DeviceConfig_Get"
    • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
      • clinfo_x64 = ""%Application Data%\ATI_Subsystem\clinfo.exe""%Application Data%\ATI_Subsystem\aticfx32.dll", ADL_Display_DeviceConfig_Get"
    • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
      • atipblag_x64 = ""%Application Data%\ATI_Subsystem\clinfo.exe""%Application Data%\ATI_Subsystem\aticfx32.dll", ADL_Display_DeviceConfig_Get"

    Step 5

    Search and delete this file

    [ 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%\ATI_Subsystem\atiadlxx.dll
    • %Application Data%\ATI_Subsystem\aticfx32.bin
    • %Application Data%\ATI_Subsystem\aticfx32.dll
    • %Application Data%\ATI_Subsystem\clinfo.exe
    • %Application Data%\ATI_Subsystem\coinst_13.152.dll
    • %Application Data%\ATI_Subsystem\racss.dat
    • %User Temp%\reader_sl.exe
    • %Windows%\Tasks\atioglxx_Ext.job
    • %User Temp%\hppscan854.pdf

    Step 6

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