Threat Encyclopedia

BKDR_PROTUX.SMZKEB-G

Publish date: June 08, 2018

ALIASES:

Trojan.Win32.Agentb.iwti (Kaspersky); Gen:Variant.Zusy.264505 (BitDefender); W32/Generic.AC.3EF98C!tr (Fortinet)

PLATFORM:

Windows

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

  • Threat Type:Backdoor

  • Destructiveness:No

  • Encrypted: Yes

  • In the wild: Yes

OVERVIEW

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 then deletes itself afterward.

It executes commands from a remote malicious user, effectively compromising the affected system.

TECHNICAL DETAILS

File Size:

89,600 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Dec 2017

Payload:

Connects to URLs/IPs

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 copies of itself into the affected system:

  • %Application Data%\cnagnt.dll
  • %User Temp%\{malware name}.exe
  • %Windows%\LINKINFO.dll
  • %User Temp%\cnagnt.dll
  • %User Temp%\ppa{Random hex value}.tmp → temporary DLL
  • %User Temp%\RCX{Random hex value}.tmp → temporary DLL

(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.. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It drops the following files:

  • %User Temp%\1.txt → Contains the malware's process information. Deleted afterwards.
  • %User Temp%\ppa{Random hex value}.tmp.vbs
  • {Malware path}\q.bat → Uninstall itself. Deleted afterwards.

(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 executes then deletes itself afterward.

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

  • tmutexabc

Autostart Technique

This Backdoor creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Conime = "%System%\rundll32" "%User Temp%\ppa{Random hex value}.tmp",Sd

It drops the following file(s) in the Windows Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\Conime.lnk
  • %User Startup%\Conime.exe

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
WaitToKillAppTimeout = 1000

Backdoor Routine

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

  • Upload victim information.
  • Execute a batch script, executable file or DLL file.

Other Details

This Backdoor connects to the following URL(s) to check for an Internet connection:

  • http://www.bing.com/

It does the following:

  • It checks for the existence of the following AV products:
    • norton
    • synmantec
    • trend micro
    • kaspersky
    • avira
    • avg
  • It checks for the existence of the following AV related processes:
    • uiseagnt.exe
    • v3ltray.exe
    • ayagent.aye
    • avp.exe
    • avgnt.exe
    • ccsvchst.exe
    • pccntmon.exe
    • cntaosmgr.exe
    • klnagent.exe
    • avg
  • If any of the AV related product is found:
    • Convert itself to a temporary DLL with a default export of ‘Dm’ in the %User Temp% directory.
    • If running with administrator privileges on a 32-bit system:
      • Copy the temporary DLL in %User Temp% to %Windows%\LINKINFO.dll
    • If not,
      • If its file name has "emp\low" in it. The malware copies the temporary DLL to %User Temp%\cnagnt.dll
      • Else, the malware copies the temporary DLL to %Application Data%\cnagnt.dll
      • Delete the temporary DLL in %User Temp%
      • Create %User Startup%\Conime.lnk that points to either
        • %System%\rundll32.exe "%Application Data%\cnagnt.dll",Sd
        • %System%\rundll32.exe "%User Temp%\cnagnt.dll",Sd
  • It connects to the following URL to download data that contains the command and control server(s) and port(s):
    • https://github.com/{BLOCKED}ff
    • http://{BLOCKED}see.tumblr.com:443

    However, as of this writing the said sites are inaccessible.
  • It adds garbage data to its copies to avoid easy detection.
  • Checks if it is running in %User Temp%. If not, it will copy itself to %User Temp% and execute the copy with the following command:
    • "%User Temp%\{malware name}.exe" {Malware path}\{Malware name}.exe

SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.382.08

FIRST VSAPI PATTERN DATE:

04 May 2017

VSAPI OPR PATTERN File:

13.383.00

VSAPI OPR PATTERN Date:

05 May 2017

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
    • Conime = "%System%\rundll32" "%User Temp%\ppa{Random hex value}.tmp",Sd
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • WaitToKillAppTimeout = 1000

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%\cnagnt.dll
  • %User Temp%\{malware name}.exe
  • %Windows%\LINKINFO.dll
  • %User Temp%\cnagnt.dll
  • %User Temp%\ppa{Random hex value}.tmp
  • %User Temp%\RCX{Random hex value}.tmp
  • %User Temp%\1.txt
  • %User Temp%\ppa{Random hex value}.tmp.vbs
  • {Malware path}\q.bat
  • %User Startup%\Conime.lnk
  • %User Startup%\Conime.exe

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_PROTUX.SMZKEB-G. 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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