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TROJ_PHASE.A

April 07, 2015
 Analysis by: Michelle Morales
 ALIASES:

Trojan.Phase (Symantec); Win32:PhaseBot-A [Trj] (Avast); a variant of Win32/Phase.A (ESET);

 PLATFORM:

Windows 7

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW


This Trojan retrieves specific information from the affected system.

  TECHNICAL DETAILS

File Size:

121,344 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

23 Feb 2015

Payload:

Collects system information, Connects to URLs/IPs

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Host Process (RunDll) = "rundll32.exe javascript:"\..\mshtml,RunHTMLApplication ";eval((new%20ActiveXObject("WScript.Shell")).RegRead("HKCU\Software\Microsoft\Active%20Setup\Installed%20Components\{unique bot GUID}\JavaScript"));close();;"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Active Setup\Installed Components\{unique bot GUID}

It adds the following registry entries:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Active Setup\Installed Components\{unique bot GUID}
JavaScript = "{B64-encrypted Java script}"

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Active Setup\Installed Components\{unique bot GUID}
Rc4Encoded32 = "{Rc4 encoded hex values}"

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Active Setup\Installed Components\{unique bot GUID}
Rc4Encoded64 = "{Rc4 encoded hex values}"

Information Theft

This Trojan retrieves the following information from the affected system:

  • User Startup folder path
  • Volume GUID of root directory
  • Computer Name
  • User Name

NOTES:

This Trojan scans for the following registry key to check the .NET Framework version:

  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\net framework setup\NDP\v2.0.50727

It scans for the following registry key to check if Windows PowerShell is installed:

  • HKEY_CLASSES_ROOT\.ps1

It executes the Java script found in the following registry:

  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\Active Setup\Installed Components\{unique bot GUID}\JavaScript

The script decodes and executes a Base64-encoded PowerShell Script if the PowerShell installed in the system is version 1.0.

The PowerShell Script decrypts an RC4-encrypted shell code specific for 64-bit and 32-bit systems. The shell code it decrypts can be found in the following registry:

  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\Active Setup\Installed Components\{72507C54-3577-4830-815B-310007F6135A}\Rc4Encoded32
  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\Active Setup\Installed Components\{72507C54-3577-4830-815B-310007F6135A}\Rc4Encoded64

The shell code does the following:

  • creates remote thread in all running processes
  • connects to the following URL to send information:
    • vcv.{BLOCKED} p.biz/gate.php

However, as of this writing, the said URL is no longer available.

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

11.496.05

FIRST VSAPI PATTERN DATE:

23 Feb 2015

VSAPI OPR PATTERN File:

11.497.00

VSAPI OPR PATTERN Date:

24 Feb 2015

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Restart in Safe Mode

[ Learn More ]

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_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Windows Host Process (RunDll) = "rundll32.exe javascript:"\..\mshtml,RunHTMLApplication ";eval((new%20ActiveXObject("WScript.Shell")).RegRead("HKCU\Software\Microsoft\Active%20Setup\Installed%20Components\{unique bot GUID}\JavaScript"));close();;"

Step 5

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.

  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\Active Setup\Installed Components\{unique bot GUID}

Step 6

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