TROJ_DLOAD.SMJO

October 18, 2013
 Modified by: Anthony Joe Melgarejo
 ALIASES:

TrojanDownloader:Win32/Leechole.B (Microsoft), Downloader-FKT!D5926EFEC414 (McAfee), W32/Leechole.G!tr (Fortinet), NSIS/TrojanDownloader.Leechole.G trojan (ESET)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet

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.

As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

49,599 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

16 Apr 2013

Payload:

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.

Installation

This Trojan adds the following folders:

  • %User Temp%\ns{random}.tmp
  • %User Temp%\Serving Turns

(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 and 7.)

It drops the following non-malicious files:

  • %User Temp%\ns{random}.tmp\NSISdl.dll
  • %User Temp%\ns{random}.tmp\System.dll
  • %User Temp%\Serving Turns\{date of execution in YYYYMMDD then 6 random digits}.ini
  • %User Temp%\Serving Turns\flag.ini
  • %User Temp%\Serving Turns\flag.txt
  • %User Temp%\ns{random 1}.tmp
  • %User Temp%\ns{random 2}.tmp

(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 and 7.)

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\MID
PIC = "{random number}"

It adds the following registry keys as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\MID

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://{BLOCKED}1c67583446.avk.co.kr/get3.php?e={random number}&tc={random number}&uid={random number}

As of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine:

9.300

VSAPI OPR PATTERN File:

9.864.09

VSAPI OPR PATTERN Date:

18 Apr 2013

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

Identify and terminate files detected as TROJ_DLOAD.SMJO

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 3

Delete this registry key

[ 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer
    • MID

Step 4

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Temp%\ns{random}.tmp
  • %User Temp%\Serving Turns

Step 5

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%\ns{random 1}.tmp
  • %User Temp%\ns{random 2}.tmp

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_DLOAD.SMJO. 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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