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TROJ_DLOADER.SML

October 10, 2013
 ALIASES:

Worm:Win32/Helompy.B (Microsoft); Generic.dx!trd (McAfee); W32.Imaut (Symantec); PAK:UPX, ARC:Embedded, [script.au3]:Worm.Win32.AutoIt.tq, [script.au3]:Worm.Win32.AutoIt.tq, [deskto (Kaspersky); Worm.Win32.AutoIt.tq (v) (Sunbelt); Worm:W32/AutoIt.AX (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • 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:

579,072 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

07 Nov 2011

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 copies of itself into the affected system:

  • %System Root%\Win\lsass.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It creates the following folders:

  • %System Root%\5a6bc696e3c4f3774aa67a47ebad3e372210fc0d_0507cffb97f4a22973aa267abbc7
  • %System Root%\Win

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
run32 = "%System Root%\Win\lsass.exe"

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\aut1.tmp
  • %User Temp%\aut2.tmp
  • %System Root%\Win\names.txt
  • %System Root%\Win\desktop.exe
  • %User Startup%\desktop.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 and 7.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %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, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://peradjoka.{BLOCKED}5.com/BRIAN-108E9A4A3/1.rar

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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

Restart in Safe Mode

[ Learn More ]

Step 3

Delete this registry value

[ 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.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • run32="%System Root%\Win\lsass.exe"

Step 4

Search and delete these folders

[ 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.
  • %System Root%\5a6bc696e3c4f3774aa67a47ebad3e372210fc0d_0507cffb97f4a22973aa267abbc7
  • %System Root%\Win

Step 5

Search and delete these components

[ Learn More ]
There may be some components 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%\aut1.tmp
  • %User Temp%\aut2.tmp
  • %System Root%\Win\names.txt
  • %System Root%\Win\desktop.exe
  • %User Startup%\desktop.exe

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DLOADER.SML. 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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