ALIASES:

Backdoor:Win32/Xyligan.B (Microsoft); HEUR:Trojan.Win32.Generic (Kaspersky); Mal/EncPk-PQ (Sophos)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 418,816 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 07 Nov 2014

Arrival Details

This backdoor 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%\eytkaz.exe

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It creates the following folders:

  • %User Profile%\Application Data\DYA_IWSFEJOJQWVURPLNU
  • %User Profile%\DYA_IWSFEJOJQWVURPLNU\1.0.0
  • %User Profile%\1.0.0\Data

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

Other System Modifications

This backdoor adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\rcmdsvc
Description = "Windows Resource Kit"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\eytkaz.exe = "%System%\eytkaz.exe:*:Enabled:Microsoft (R) Internetal IExplore"

Dropping Routine

This backdoor drops the following files:

  • %User Profile%\Data\app.dat
  • %User Profile%\Data\updates.dat
  • %User Profile%\Data\dya.dat
  • %User Profile%\Application Data:$SS_DESCRIPTOR_SBXNV9VVGV1BFNB4NF9X4N6HK0ST3K01F4SBHT0FSPF7VBCVPJGF
  • %User Profile%\DYA_IWSFEJOJQWVURPLNU\1.0.0:$SS_DESCRIPTOR_SBXNV9VVGV1BFNB4NF9X4N6HK0ST3K01F4SBHT0FSPF7VBCVPJGF
  • %Desktop%:$SS_DESCRIPTOR_SBXNV9VVGV1BFNB4NF9X4N6HK0ST3K01F4SBHT0FSPF7VBCVPJGF

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop in Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}0

It deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.700

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 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\rcmdsvc
    • Description = "Windows Resource Kit"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %System%\eytkaz.exe = "%System%\eytkaz.exe:*:Enabled:Microsoft (R) Internetal IExplore"

Step 3

Search and delete these components

[ Learn More ]
There may be some components that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Profile%\Data\app.dat
  • %User Profile%\Data\updates.dat
  • %User Profile%\Data\dya.dat
  • %User Profile%\Application Data:$SS_DESCRIPTOR_SBXNV9VVGV1BFNB4NF9X4N6HK0ST3K01F4SBHT0FSPF7VBCVPJGF
  • %User Profile%\DYA_IWSFEJOJQWVURPLNU\1.0.0:$SS_DESCRIPTOR_SBXNV9VVGV1BFNB4NF9X4N6HK0ST3K01F4SBHT0FSPF7VBCVPJGF
  • %Desktop%:$SS_DESCRIPTOR_SBXNV9VVGV1BFNB4NF9X4N6HK0ST3K01F4SBHT0FSPF7VBCVPJGF

Step 4

Search and delete these folders

[ 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.
  • %User Profile%\Application Data\DYA_IWSFEJOJQWVURPLNU
  • %User Profile%\DYA_IWSFEJOJQWVURPLNU\1.0.0
  • %User Profile%\1.0.0\Data

Step 5

Scan your computer with your Trend Micro product to delete files detected as BKDR_XYLIGAN.PVJ. 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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