Analysis by: Rika Joi Gregorio
ALIASES:

W32/Backdoor.J.gen!Eldorado(FProt), Backdoor.Win32.Rbot.aeug(Kaspersky), Trojan:Win32/Delf.EZ(Microsoft), Trojan.Win32.Delf.ez (v)(Sunbelt)

 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: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This backdoor may arrive bundled with malware packages as a malware component. It 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: 129,024 bytes
File Type: DLL
Memory Resident: Yes
Initial Samples Received Date: 20 May 2013

Arrival Details

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

It 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 backdoor drops the following copies of itself into the affected system:

  • %System%\Virtual.dll

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

Autostart Technique

This backdoor 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\Network Virtual
ImagePath = "%System%\svchost.exe -k netsvcs"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network Virtual\Parameters
ServiceDll = "%System%\Virtual.dll"

It is a .DLL file that adds the following services:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network Virtual

Other System Modifications

This backdoor adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Setup
1728333415332E2B202F = "1728333415332E2B202F"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}212.{BLOCKED}p.net
  • http://{BLOCKED}u.{BLOCKED}6.org

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.936.06
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

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
    • Network Virtual

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\Setup
    • 1728333415332E2B202F = "1728333415332E2B202F"

Step 5

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