Analysis by: John Anthony Banes
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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

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 executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system. As of this writing, the said sites are inaccessible.

It connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size: 1,435,136 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 04 Dec 2018
Payload: Connects to URLs/IPs, Downloads files, Executes files

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 copies of itself into the affected system:

  • %Windows%\windefender.exe

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

It creates the following folders:

  • %Windows%\rss

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

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\WinDefender

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\WinDefender\Security

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\WinDefender
Type = 16

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\WinDefender
Start = 2

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\WinDefender
ErrorControl = 1

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\WinDefender
ImagePath = %Windows%\windefender.exe

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\WinDefender
DisplayName = Windows Defender Helper Service (Windows 1703 Creators Update)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\WinDefender
ObjectName = LocalSystem

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\WinDefender\Security
Security = {hex values}

HKEY_CURRENT_USER\Software\Microsoft\
TestApp
ServiceVersion = 0.5

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://{BLOCKED}ndmusic.com/app/app.exe

It saves the files it downloads using the following names:

  • %Windows%\rss\csrss.exe

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

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

As of this writing, the said sites are inaccessible.

Other Details

This Trojan connects to the following website to send and receive information:

  • {"Servers" string value in HKEY_CURRENT_USER\Software\Microsoft\TestApp}/bots/log

It does the following:

  • It requires the following registry key in order to proceed with its routines:
    • HKEY_CURRENT_USER\Software\Microsoft\TestApp
  • It executes the the following command to modify malware's security descriptor:
    sc sdset WinDefender D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;CCDCLCSWRPLOCRSDRCWDWO;;;BA)(D;;WPDT;;;BA)(A;;CCLCSWLOCRRC;;;IU)(A;;CCLCSWLOCRRC;;;SU)S:(AU;FA;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;WD);

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 14.666.03
FIRST VSAPI PATTERN DATE: 04 Dec 2018
VSAPI OPR PATTERN File: 14.667.00
VSAPI OPR PATTERN Date: 05 Dec 2018

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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services
    • WinDefender
  • In HKEY_CURRENT_USER\Software\Microsoft
    • TestApp

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.
  • %Windows%\rss\csrss.exe

Step 6

Search and delete this folder

[ 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.
  • %Windows%\rss

Step 7

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