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BKDR_LOWBALL.A

December 18, 2015
 Analysis by: Sammy Chua
 ALIASES:

Backdoor.Win32.LowBall (Ikarus)

 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

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 does not have any propagation routine.

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

As of this writing, the said sites are inaccessible.

It gathers information and reports it to its servers.

  TECHNICAL DETAILS

File Size:

20,480 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

01 Dec 2015

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.

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

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

  • arbitrary batch scripts

Download Routine

This backdoor accesses the following websites to download files:

  • https://api-content.dropbox.com/1/files/auto/{BLOCKED}om
  • https://api-content.dropbox.com/1/files/auto/{BLOCKED}om.bat
  • https://api-content.dropbox.com/1/{BLOCKED}/{machine name}?overwrite=True
  • https://api.dropbox.com/1/{BLOCKED}s/delete
  • https://api-content.dropbox.com/1/{BLOCKED}/{machine name}_{file name}
    where {file name} can be upload.bat, period.txt, silent.txt

It saves the files it downloads using the following names:

  • %User Temp%\WmiApCom
  • %User Temp%\WmiApCom.bat
  • %User Temp%\onlineflagfile
  • %User Temp%\upload
  • %User Temp%\upload.bat
  • %User Temp%\download
  • %User Temp%\period.txt
  • %User Temp%\silent.txt

(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.)

As of this writing, the said sites are inaccessible.

Other Details

This backdoor gathers the following information and reports it to its servers:

  • machine name
  • information obtainable via batch script

NOTES:

This backdoor uses a legitimate cloud-storage service to act as the C&C server.

It uses the Dropbox API with the following hard-coded bearer access token:

Authorization: Bearer sgKddaX_ntAAAAAAAAAADVYeex9Pc0NuhGII10uLUhy-Kte7gEehQSxjYgRB2yWT

It must be executed with "-st" as its parameter to start its backdoor routine.

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.196.05

FIRST VSAPI PATTERN DATE:

07 Dec 2015

VSAPI OPR PATTERN File:

12.197.00

VSAPI OPR PATTERN Date:

08 Dec 2015

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

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.  
  • %User Temp%\WmiApCom
  • %User Temp%\WmiApCom.bat
  • %User Temp%\onlineflagfile
  • %User Temp%\upload
  • %User Temp%\upload.bat
  • %User Temp%\download
  • %User Temp%\period.txt
  • %User Temp%\silent.txt

Step 5

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

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_LOWBALL.A. 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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