TROJ_DELF.HEK


 ALIASES:

Generic.dx!gaw (McAfee); Infostealer (Symantec); Trojan.Win32.Agent.stmk (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan.Generic.276159 (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:

256,066 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

22 Nov 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 adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
WebsaleSystem = "%Program Files%\WebsaleSystem\WebsAgent.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\Software\WebsaleSystem

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\websale.co.kr

HKEY_CLASSES_ROOT\CLSID\InprocServer32

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\WebsaleSystem
WebsaleSystem = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects
NoExplorer = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\websale.co.kr
http = "2"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\websale.co.kr
https = "2"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\InprocServer32
ThreadingModel = "Apartment"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
MaxConnectionsPerServer = "a"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
MaxConnectionsPer1_0Server = "a"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects
NoExplorer = "1"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
Zones\3
1A10 = "0"

(Note: The default value data of the said registry entry is 1.)

It deletes the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Ext\
Settings\{C533ADF1-0C80-11D1-8C54-00A02468F316}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Ext\
Settings\{BDD307C3-7BC0-4542-9F8F-A9611FE6C1BF}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Ext\
Settings\{B1549E58-3894-11D2-BB7F-00A0C999C4C1}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Ext\
Settings\{754FF233-5D4E-11D2-875B-00A0C93C09B3}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Ext\
Settings

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

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\Software
    • WebsaleSystem
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer
    • Browser Helper Objects
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains
    • websale.co.kr
  • In HKEY_CLASSES_ROOT\CLSID\
    • InprocServer32
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer
    • Browser Helper Objects

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\CurrentVersion\Run
    • WebsaleSystem = "%Program Files%\WebsaleSystem\WebsAgent.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\WebsaleSystem
    • WebsaleSystem = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects
    • NoExplorer = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains\websale.co.kr
    • http = "2"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains\websale.co.kr
    • https = "2"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\InprocServer32
    • ThreadingModel = "Apartment"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • MaxConnectionsPerServer = "a"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • MaxConnectionsPer1_0Server = "a"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects
    • NoExplorer = "1"

Step 5

Restore this modified 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3
    • From: 1A10 = "0"
      To: 1A10 = ""1""

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DELF.HEK. 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 these deleted registry keys/values from backup

*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Ext\Settings
    • {C533ADF1-0C80-11D1-8C54-00A02468F316}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Ext\Settings
    • {BDD307C3-7BC0-4542-9F8F-A9611FE6C1BF}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Ext\Settings
    • {B1549E58-3894-11D2-BB7F-00A0C999C4C1}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Ext\Settings
    • {754FF233-5D4E-11D2-875B-00A0C93C09B3}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Ext
    • Settings


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