TROJ_DOCDLODR.T

October 25, 2014
 Analysis by: Jaime Benigno Reyes
 ALIASES:

TrojanDownloader:W97M/Ledod.O (Microsoft); Trojan-Downloader.MSWord.Agent.by (Kaspersky); [word/vbaProject.bin]:W97M/Downloader (McAfee)

 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:

Spammed via email, Downloaded from the Internet, Dropped by other malware

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

  TECHNICAL DETAILS

File Size:

Varies

File Type:

DOC

Initial Samples Received Date:

22 Oct 2014

Payload:

Connects to URLs/IPs, Downloads files

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.

Installation

This Trojan drops the following files:

  • {malware path}\ntusersc.ps1 - used to download and execute crsss2.exe
  • {malware path}\ntuserskk.vbs - used to execute the following command:
    • POWERSHELL.EXE -EXECUTIONPOLICY BYPASS -NOPROFILE -FILE "{malware path}\ntusersc.ps1",0,TRUE
  • {malware path}\ntusersss.bat - used to execute the created ntuserskk.vbs

Download Routine

This Trojan accesses the following websites to download files:

  • http://{BLOCKED}.{BLOCKED}.234.167:8080/gr/4.exe

It saves the files it downloads using the following names:

  • {malware path}\crsss2.exe - detected as TROJ_KRYPTIK.AABA

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

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

11.228.05

FIRST VSAPI PATTERN DATE:

22 Oct 2014

VSAPI OPR PATTERN File:

11.229.00

VSAPI OPR PATTERN Date:

23 Oct 2014

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

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.  
  • {malware path}\crsss2.exe
  • {malware path}\ntusersc.ps1
  • {malware path}\ntuserskk.vbs
  • {malware path}\ntusersss.bat

Step 3

Scan your computer with your Trend Micro product to delete files detected as TROJ_DOCDLODR.T. 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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