Analysis by: Byron Jon Gelera
 Modified by: Michael Jay Villanueva
ALIASES:

TrojanDownloader:JS/Rezopec.A (Microsoft); JS.Downloader.G (Symantec); JS/Nemucod.BZN!tr.dldr (Fortinet)

 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, Spammed via email

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It 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 does not have any backdoor routine.

As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 137,002 bytes
File Type: Other
Memory Resident: No
Initial Samples Received Date: 18 Jan 2017
Payload: Connects to URLs/IPs, Displays message/message boxes

Arrival Details

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It 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 Trojan does not have any propagation routine.

Backdoor Routine

This Trojan does not have any backdoor routine.

Download Routine

This Trojan accesses the following websites to download files:

  • http://{BLOCKED}droperez.com/fotos/photos/xfs_extension.exe

It saves the files it downloads using the following names:

  • {Path Assigned by the User}\{Filename assigned by the User}.exe
    Note: The Default Filename is "xfs_extension.exe"

As of this writing, the said sites are inaccessible.

Other Details

This Trojan does the following:

  • Upon running the malware on a browser, it will connect to the URL mentioned above and will display a download window where the user can set the path and filename of the downloaded file manually.

NOTES:

This malware displays the following image on the browser:

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 13.164.03
FIRST VSAPI PATTERN DATE: 18 Jan 2017
VSAPI OPR PATTERN File: 13.165.00
VSAPI OPR PATTERN Date: 19 Jan 2017

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

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.
  • {Path Assigned by User}\{Filename assigned by the User}.exe - Default name is xfs_extension.exe

Step 4

Scan your computer with your Trend Micro product to delete files detected as JS_NEMUCOD.MM. 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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