Analysis by: Jimelle Monteser
ALIASES:

a variant of Win64/Rootkit.Kryptik.L (NOD32), Backdoor.Necurs (Norton)

 PLATFORM:

Windows XP (64-bit), Windows Vista (64-bit), Windows 7 (64-bit)

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan may arrive bundled with malware packages as a malware component.

Its rootkit functionalities are used by other malware/grayware.

It requires its main component to successfully perform its intended routine. It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 79,824 bytes
File Type: SYS
Memory Resident: Yes
Initial Samples Received Date: 14 Mar 2014

Arrival Details

This Trojan may arrive bundled with malware packages as a malware component.

Installation

This Trojan drops the following copies of itself into the affected system:

  • %System%\drivers\{random filename}.sys

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

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{malware filename}

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{malware filename}\
0000

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{malware filename}\
0000\Control

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{random filename}

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{random filename}\
0000

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{random filename}\
0000\Control

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\{random filename}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{malware filename}
NextInstance = "1"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{malware filename}\
0000
Legacy = "1"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{malware filename}\
0000\Control
*NewlyCreated* = "0"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{malware filename}\
0000\Control
ActiveService = "1"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{malware filename}\
0000
Service = "{malware filename}"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{malware filename}\
0000\Control
ActiveService = "{malware filename}"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{random filename}
NextInstance = "1"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{random filename}\
0000
Legacy = "1"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{random filename}\
0000
Service = "{random filename}"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{random filename}\
0000\Control
*NewlyCreated* = "0"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_{random filename}\
0000\Control
ActiveService = "{random filename}"

Rootkit Capabilities

This Trojan s rootkit functionalities are used by other malware/grayware.

Other Details

This Trojan requires its main component to successfully perform its intended routine.

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 10.678.04
FIRST VSAPI PATTERN DATE: 21 Mar 2014
VSAPI OPR PATTERN File: 10.679
VSAPI OPR PATTERN Date: 22 Mar 2014

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 and note files detected as RTKT64_NECURS.YUU

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\ControlSet001\Enum\Root
    • LEGACY_{malware filename}
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Enum\Root
    • LEGACY_{random filename}
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services
    • {random filename}

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RTKT64_NECURS.YUU. 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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