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TROJ_NECURS.BGTB

April 24, 2014
 ALIASES:

Trojan:Win32/Necurs (Microsoft); Trojan-Dropper.Win32.Necurs.ulu (Kaspersky); Mal/Generic-L (Sophos); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Crypt3.JXJ (AVG)

 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:

73,216 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

24 Apr 2014

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:

  • %Windows%\Installer\{18776C0E-F937-7AC6-D4AE-5844B30689C2}\syshost.exe

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

It creates the following folders:

  • %Windows%\Installer\{18776C0E-F937-7AC6-D4AE-5844B30689C2}

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

Other System Modifications

This Trojan deletes the following files:

  • {malware path and file name}.tmp
  • %Windows%\Installer\{18776C0E-F937-7AC6-D4AE-5844B30689C2}\syshost.exe:Zone.Identifier
  • %Windows%\Installer\{18776C0E-F937-7AC6-D4AE-5844B30689C2}\syshost.exe.tmp
  • %User Temp%\f36b13f.tmp

(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %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 adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32\Security

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32
Type = "1"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32
ErrorControl = "0"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32
ImagePath = "%Windows%\Installer\{18776C0E-F937-7AC6-D4AE-5844B30689C2}\syshost.exe /service"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32\Security
Security = "{random values}"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32
ObjectName = "LocalSystem"

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

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

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\ControlSet001\Services
    • syshost32
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\syshost32
    • Security

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\SYSTEM\ControlSet001\Services\syshost32
    • Type = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\syshost32
    • Start = "2"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\syshost32
    • ErrorControl = "0"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\syshost32
    • ImagePath = "%Windows%\Installer\{18776C0E-F937-7AC6-D4AE-5844B30689C2}\syshost.exe /service"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\syshost32\Security
    • Security = "{random values}"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\syshost32
    • ObjectName = "LocalSystem"

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.
  • %Windows%\Installer\{18776C0E-F937-7AC6-D4AE-5844B30689C2}

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_NECURS.BGTB. 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 6

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.

  • {malware path and file name}.tmp
  • %Windows%\Installer\{18776C0E-F937-7AC6-D4AE-5844B30689C2}\syshost.exe:Zone.Identifier
  • %Windows%\Installer\{18776C0E-F937-7AC6-D4AE-5844B30689C2}\syshost.exe.tmp
  • %User Temp%\f36b13f.tmp


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