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TROJ_DELF.SGF

May 28, 2013
 Analysis by: Nikko Tamana
 ALIASES:

Virus.Win32.Gamona (Ikarus), Trojan:Win32/Delf.EZ (Microsoft)

 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:

  • 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:

77,312 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

23 May 2013

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%\Sesion.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion\Parameters
ServiceDll = "%System%\Sesion.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion\Parameters

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion\Security

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion\Enum

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion
Type = "110"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion
ErrorControl = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion
ImagePath = "%SystemRoot%\System32\svchost.exe -k netsvcs"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion
DisplayName = "Serial Number Help Sesion"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion
Description = "ά»¤ÍøÂçÉϼÆËã»úµÄ¸üÐÂÁÐ±í£¬²¢½«ÁбíÌṩ¸ø¼ÆËã»úÖ¸¶¨ä¯ÀÀ¡£"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion\Security
Security = "{Hex Values}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion\Enum
0 = "Root\LEGACY_HELP_SESION\0000"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion\Enum
Count = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Help Sesion\Enum
NextInstance = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Setup
0F2435362E332A = "0F2435362E332A"

Other Details

This Trojan connects to the following possibly malicious URL:

  • 494026212.{BLOCKED}p.net
  • yantou.{BLOCKED}6.org

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.936.07

FIRST VSAPI PATTERN DATE:

23 May 2013

VSAPI OPR PATTERN File:

9.937.00

VSAPI OPR PATTERN Date:

24 May 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

Scan your computer with your Trend Micro product to delete files detected as TROJ_DELF.SGF. 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 3

Restart in Safe Mode

[ Learn More ]

Step 4

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
    • Help Sesion

Step 5

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\Setup
    • 0F2435362E332A = "0F2435362E332A"

Step 6

Search and delete the files detected as TROJ_DELF.SGF

*Note: Some component files may be 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.

To stop the malware/grayware from running when certain files are opened:

For Windows 2000, Windows XP, and Windows Server 2003:

  1. Right-click Start then click Search....
  2. In the Named input box, type the name of the file that was detected earlier.
  3. In the Look In drop-down list, select My Computer then press Enter.
  4. Once located, select the file then press SHIFT+DELETE to delete it.

For Windows Vista and Windows 7:

  1. Click Start>Computer.
  2. In the Search Computer input box, type the name of the file detected earlier, and press Enter.
  3. Once located, select the file then press SHIFT+DELETE to delete it.
    *Note: Read the following Microsoft page if these steps do not work on Windows 7.

Step 7

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