Trojan.JS.TWINFLOWER.A

April 02, 2020
 Analysis by: Bren Matthew Ebriega
 ALIASES:

Trojan-Downloader:JS/TeslaCrypt.C (FSECURE)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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 requires its main component to successfully perform its intended routine. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

8,650 bytes

File Type:

JS

Memory Resident:

No

Initial Samples Received Date:

27 Mar 2020

Payload:

Connects to URLs/IPs, Modifies system registry

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.

Download Routine

This Trojan downloads the file from the following URL and renames the file when stored in the affected system:

  • http://{BLOCKED}.{BLOCKED}.37.73:8099/ssd_cfg.db

It saves the files it downloads using the following names:

  • %User Temp%\WinRAR\elements162816.db

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Other Details

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
WCCloud
cfg = {encoded value}

It requires its main component to successfully perform its intended routine.

It checks for the presence of the following process(es):

  • wireshark.exe
  • fiddler.exe
  • httpanalyze
  • HipsDaemon
  • softice.exe
  • windgb.exe
  • dbg.exe
  • tcpmon
  • networktrafficview.exe
  • hookme.exe
  • sniff.exe
  • chkencap.exe
  • wsockexpert

It does the following:

  • It does not perform its download routine if any of the processes are detected running in the affected system
  • Connects to the following URL's:
    • http://yky.{BLOCKED}e.com:38275/api/cload.asp?sid={numbers}
    • https://{BLOCKED}a.{BLOCKED}1.la/go1?id=20625191&rt={numbers}&rl=1280*1024&lang=zh-CN&ct=unknow&pf=1&ins=1&vd=1&ce=1&cd=32&ds=hello&ing=1&ekc=&sid={numbers}&tt=hello&kw=hello&cu=https:\\{BLOCKED}o.{BLOCKED}u.com&pu=https:\\{BLOCKED}o.{BLOCKED}u.com
    • https://{BLOCKED}a.{BLOCKED}1.la/go1?id=20625191&rt={numbers}&rl=1280*1024&lang=zh-CN&ct=unknow&pf=1&ins=1&vd=1&ce=1&cd=32&ds=hello&ing=1&ekc=&sid={numbers}&tt=hello&kw=hello&cu=https:\\www.{BLOCKED}u.com\{value}&pu=https:\\www.{BLOCKED}u.com\{value}

However, as of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.780.03

FIRST VSAPI PATTERN DATE:

02 Apr 2020

VSAPI OPR PATTERN File:

15.781.00

VSAPI OPR PATTERN Date:

03 Apr 2020

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 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

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\WCCloud
    • cfg = {encoded value}

Step 4

Scan your computer with your Trend Micro product to delete files detected as Trojan.JS.TWINFLOWER.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 the following Trend Micro Support pages for more information:


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