BKDR_MISDAT.AB

 Modified by: Sammy Chua

 ALIASES:

Backdoor:Win32/Misdat.A!dha (Microsoft); Trojan.Gen.SMH (Symantec); RDN/Generic BackDoor!bd3 (McAfee)

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

  TECHNICAL DETAILS

File Size:

70,144 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

02 Jul 2015

Payload:

Steals information

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 non-malicious files:

  • %AppDataLocal%\{random file name 2}.tmp -> is deleted afterwards
  • %AppDataLocal%\{random file name1}.tmp -> is deleted afterwards

(Note: %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local 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 copies of itself into the affected system:

  • %Application Data%\{unique identifier}\mstdc.exe - if the username is not "system"(case-insensitive)
  • %Common AppData%\{unique identifier}\mstdc.exe - if the username is "system"(case-insensitive)

(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 creates the following folders:

  • %Application Data%\{unique identifier} - if the username is not "system"(case-insensitive)
  • %Common AppData%\{unique identifier} - if the username is "system"(case-insensitive)

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

  • {unique identifier}_KB10B2D1_CIlFD2C

Autostart Technique

This backdoor drops the following shortcut pointing to its copy in the User Startup folder to enable its automatic execution at every system startup:

  • %Common Startup%\Realtek_{unique identifier}.lnk -> targets the copy of the malware with "/Start" as command line argument

(Note: %Common Startup% is the system's shared Startup folder, which is usually C:\Documents and Settings\All Users\Start Menu\Programs\Startup on Windows 2000, XP, and Server 2003.)

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\AdobeSoft -> is deleted afterwards

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Recovery

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\ssl.projectscorp.net

It adds the following registry entries:

HKEY_CURRENT_USER\Software\AdobeSoft
IMJPMIJ8.1{first 3 nybbles of unique identifier} = "%Application Data%\{unique identifier}\msdtc.exe /Start"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Recovery
AutoRecover = "2"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\ssl.projectscorp.net
http = "2"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\ssl.projectscorp.net
https = "2"

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
IMJPMIJ8.1{first 3 nybbles of unique identifier} = "%Application Data%\{unique identifier}\msdtc.exe /Start"

Backdoor Routine

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

  • Download arbitrary file and execute
  • Delete File

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • news.{BLOCKED}ow.com:80//Item/{random}.asp
  • ssl.{BLOCKED}scorp.net/pic/index.asp

Information Theft

This backdoor gathers the following data:

  • Computer Name
  • Operating System
  • User Name
  • User Group
  • add user test result
  • create directory test result
  • open service manager test result
  • File System
  • Auto Config URL
  • Proxy Address
  • List of Services
  • IP Configuration
  • List of Users

NOTES:

The malware checks if the machine uses a Japanese keyboard using the GetKeyboardType API.

The {unique identifier} is composed of eight hexadecimal numbers computed from the volume serial number, computer name, and other system information.

If the username is not system, the malware attempts to create its autostart registry using the following steps:

  • Backup the registry key HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run to %AppDataLocal%\{random file name1}.tmp
  • Create the registry key HKEY_CURRENT_USER\Software\AdobeSoft
  • Restore the registry data in %AppDataLocal%\{random file name1}.tmp to HKEY_CURRENT_USER\Software\AdobeSoft
  • Adds IMJPMIJ8.1{first 3 nybbles of unique identifier} = %Application Data%\{unique identifier}\msdtc.exe /Start registry entry to HKEY_CURRENT_USER\Software\AdobeSoft
  • Backup the registry key HKEY_CURRENT_USER\Software\AdobeSoft to %AppDataLocal%\{random file name2}.tmp
  • Restore the registry data in %AppDataLocal%\{random file name2}.tmp to HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  • Delete the registry key HKEY_CURRENT_USER\Software\AdobeSoft
  • Delete the temporary files %AppDataLocal%\{random file name1}.tmp and %AppDataLocal%\{random file name2}.tmp

It executes its dropped copy with the following command line argument:

/ok

It does the add user test by using NetUserAdd and NetUserDel with the strings LOST_{unique identifier} pond~!@{unique identifier}. It does the create folder test by creating and deleting the folder %System%\{unique identifier}. It does the open service manager test by calling the OpenSCManagerA API.

It creates the following process as part of its backdoor routine:

%Program Files%\internet explorer\iexplore.exe http://ssl.{BLOCK}tscorp.net/pic/index.asp?mmid={unique identifier}

It connects to the following possibly malicious URL:

  • ssl.projectscorp.net/pic/{unique identifier}.txt

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.766.05

FIRST VSAPI PATTERN DATE:

02 Jul 2015

VSAPI OPR PATTERN File:

11.767.00

VSAPI OPR PATTERN Date:

03 Jul 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

Delete this registry key

[ 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
    • AdobeSoft
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer
    • Recovery
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains
    • ssl.projectscorp.net

Step 5

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
    • IMJPMIJ8.1{first 3 nybbles of unique identifier} = "%Application Data%\{unique identifier}\msdtc.exe /Start"

Step 6

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %Application Data%\{unique identifier}
  • %Common AppData%\{unique identifier}

Step 7

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.
  • %Common Startup%\Realtek_{unique identifier}.lnk
  • %AppDataLocal%\{random file name 2}.tmp
  • %AppDataLocal%\{random file name1}.tmp

Step 8

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