Analysis by: John Donnie Celestre
ALIASES:

TrojanDownloader:JS/Nemucod (MICROSOFT); Trojan-Downloader.JS.Nemucod (IKARUS)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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.

  TECHNICAL DETAILS

File Size: 15,147 bytes
File Type: JS
Memory Resident: Yes
Initial Samples Received Date: 05 Nov 2018

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 file(s)/component(s):

  • %User Temp%\{malware filename}.js
  • %AppDataLocal%\{randomly generated chars}
  • %AppDataLocal%\{randomly generated chars}\{random chars}
  • %AppDataLocal%\{randomly generated chars}\{random chars}.js
  • %AppDataLocal%\{randomly generated chars}\{random chars}.exe

(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, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.. %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local on Windows Vista, 7, and 8.)

It adds the following processes:

  • "%System%\wscript.exe" "%User Temp%\{malware filename}.js" {randomly generated parameter}
  • "%System%\cmd.exe" /c del /F /S /Q "%AppDataLocal%\{randomly generated chars}\*.exe"
  • "%AppDataLocal%\{randomly generated chars}\{random chars}.exe" "%User Temp%\{malware filename}.js" {randomly generated parameter}

(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, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.. %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local on Windows Vista, 7, and 8.)

Autostart Technique

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

  • %All Users Profile%\Microsoft\Windows\Start Menu\Programs\Startup\Start.lnk
  • %User Startup%\Start.lnk

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000, XP, and Server 2003, or C:\ProgramData on Windows Vista, 7, and 8. . %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows XP, or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}it.com/0.html
  • http://{BLOCKED}ille.com/0.html
  • http://{BLOCKED}ille.com/2.html

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 14.608.08
FIRST VSAPI PATTERN DATE: 05 Nov 2018
VSAPI OPR PATTERN File: 14.609.00
VSAPI OPR PATTERN Date: 06 Nov 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

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%\{malware filename}.js
  • %AppDataLocal%\{randomly generated chars}
  • %AppDataLocal%\{randomly generated chars}\{random chars}
  • %AppDataLocal%\{randomly generated chars}\{random chars}.js
  • %AppDataLocal%\{randomly generated chars}\{random chars}.exe

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJAN.JS.NEMUCOD.AH. 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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