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TROJ_SMALL.SMJD

October 13, 2012
 ALIASES:

TrojanDownloader:Win32/Drstwex.A (Microsoft); Generic Dropper.ze (McAfee); Trojan.Gen (Symantec); Trojan-Downloader.Win32.Small.cdcm (Kaspersky); Trojan.Win32.Drwex.ab (v) (Sunbelt); Gen:Variant.Kazy.21497 (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:

13,120 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

21 Jul 2012

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.

Autostart Technique

This Trojan registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\.ipsec

Other System Modifications

This Trojan deletes the following files:

  • %System%\crt.dat
  • %User Profile%\wevtapi.dll
  • %User Profile%\taskmgr.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.. %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

It adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\dimsntfy32

HKEY_LOCAL_MACHINE\Software\Classes\
Interface\{5171463b-76a3-9033-2274-75c8f0a0edb6}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32
DllName = "mdhcp32.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32
Startup = "WinStart2EX"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32
Logoff = "WinOff2EX"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32
Shutdown = "WinOff2EX"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32
Asynchronous = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mdhcp32
Impersonate = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\dimsntfy32
DllName = "dimsntfy32.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\dimsntfy32
Startup = "WinStart"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\dimsntfy32
StartScreenSaver = "WinSS"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\dimsntfy32
StopScreenSaver = "WinSS"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\dimsntfy32
Asynchronous = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\dimsntfy32
Impersonate = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{5171463b-76a3-9033-2274-75c8f0a0edb6}
u = "96"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\.ipsec
Type = "1"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\.ipsec
Start = "3"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\.ipsec
ImagePath = "\?"

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\_1.tmp
  • %User Temp%\_2.tmp
  • %User Temp%\_3.tmp
  • sname
  • %System%\shimg.dll
  • %System%\dll.dll
  • %System%\dimsntfy32.dll
  • U
  • L
  • ACPI#PNP0303#2&da1a3ff&0\L\suianxvn
  • ACPI#PNP0303#2&da1a3ff&0\@

(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.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Restart in Safe Mode

[ Learn More ]

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.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services
    • .ipsec
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify
    • mdhcp32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify
    • dimsntfy32
  • In HKEY_LOCAL_MACHINE\Software\Classes\Interface
    • {5171463b-76a3-9033-2274-75c8f0a0edb6}

Step 4

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 NT\CurrentVersion\Winlogon\Notify\mdhcp32
    • DllName = "mdhcp32.dll"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\mdhcp32
    • Startup = "WinStart2EX"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\mdhcp32
    • Logoff = "WinOff2EX"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\mdhcp32
    • Shutdown = "WinOff2EX"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\mdhcp32
    • Asynchronous = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\mdhcp32
    • Impersonate = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\dimsntfy32
    • DllName = "dimsntfy32.dll"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\dimsntfy32
    • Startup = "WinStart"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\dimsntfy32
    • StartScreenSaver = "WinSS"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\dimsntfy32
    • StopScreenSaver = "WinSS"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\dimsntfy32
    • Asynchronous = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\dimsntfy32
    • Impersonate = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{5171463b-76a3-9033-2274-75c8f0a0edb6}
    • u = "96"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\.ipsec
    • Type = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\.ipsec
    • Start = "3"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\.ipsec
    • ImagePath = "\?"

Step 5

Search and delete these files

[ Learn More ]
There may be some component 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%\_1.tmp
  • %User Temp%\_2.tmp
  • %User Temp%\_3.tmp
  • sname
  • %System%\shimg.dll
  • %System%\dll.dll
  • %System%\dimsntfy32.dll
  • U
  • L
  • ACPI#PNP0303#2&da1a3ff&0\L\suianxvn
  • ACPI#PNP0303#2&da1a3ff&0\@

Step 6

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

Step 7

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %System%\crt.dat
  • %User Profile%\wevtapi.dll
  • %User Profile%\taskmgr.exe


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