Analysis by: RonJay Kristoffer Caragay
ALIASES:

Trojan:VBS/Nusdimm.A (Microsoft); VBS/Downloader-CTT (McAfee); VBS.Dunihi (Symantec);

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

  TECHNICAL DETAILS

File Size: 9,274 bytes
File Type: VBS
Memory Resident: No
Initial Samples Received Date: 04 Nov 2014
Payload: Connects to URLs/IPs, Downloads 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.

Download Routine

This Trojan accesses the following websites to download files:

  • http://www.{BLOCKED}n.com/class/index1.html

It saves the files it downloads using the following names:

  • {malware's path}\adbcall.exe

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

Other Details

This Trojan does the following:

  • It searches for the following under all subdirectories of %User Profile%\AppData\Local\Microsoft\Windows:
    • apr0423[1].dat
  • it copies found apr0423[1].dat to {malware's path}\adbcall.exe
  • it deletes {malware's path}\adbcall.exe if already exist

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

NOTES:

apr0423[1].dat was possibly created when it accessed http://www.{BLOCKED}n.com/class/index1.html , however, as of this writing apr0423[1].dat was already not available.

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 11.256.03
FIRST VSAPI PATTERN DATE: 04 Nov 2014
VSAPI OPR PATTERN File: 11.257.00
VSAPI OPR PATTERN Date: 04 Nov 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

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.
  • {malware's path}\adbcall.exe
  • apr0423[1].dat

Step 4

Scan your computer with your Trend Micro product to delete files detected as VBS_KRYPTIK.XXPU. 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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