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TROJ_FLYSTUDI.AN

June 18, 2013
 ALIASES:

Backdoor:Win32/FlyAgent.E (Microsoft); BackDoor-DRV.gen.c (McAfee); Backdoor.Trojan (Symantec); Trojan-Spy.Win32.FlyStudio.dks (Kaspersky); Backdoor.Win32.FlyAgent.h (v) (Sunbelt); Trojan horse BackDoor.FlyAgent.F (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.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

797,728 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

13 Jun 2013

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 creates the following folders:

  • %User Temp%\E_4

(Note: %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.)

Autostart Technique

This Trojan registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\boorserver\Parameters

Other System Modifications

This Trojan deletes the following files:

  • %System Root%\DEL_FI~1.BAT

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It adds the following registry keys:

HKEY_CURRENT_USER\Software\FlySky\
E\Install

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Check_Associations = "NO"

HKEY_CURRENT_USER\Software\FlySky\
E\Install
Path = "%User Temp%\E_4"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\boorserver\Parameters
Application = "%System%\boorcservice.exe"

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\E_4\krnln.fnr
  • %User Temp%\E_4\Exmlrpc.fne
  • %User Temp%\E_4\dp1.fne
  • %System%\boorcservice.exe
  • %System Root%\del_file_b.bat
  • %System%\boorcservice.dll
  • %User Temp%\_eviip.tmp
  • %User Temp%\e_4\boordc7ac.dll
  • %Windows%\Fonts\09e84031a107f84a8d2ad6cdfb3b06b5.dat
  • %User Temp%\E_4\krnln.fne

(Note: %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.. %System% is the Windows system folder, which is usually C:\Windows\System32.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %Windows% is the Windows folder, which is usually C:\Windows.)

Other Details

This Trojan deletes itself after execution.

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

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\boorserver
    • Parameters
  • In HKEY_CURRENT_USER\Software\FlySky\E
    • Install

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\Internet Explorer\Main
    • Check_Associations = "NO"
  • In HKEY_CURRENT_USER\Software\FlySky\E\Install
    • Path = "%User Temp%\E_4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\boorserver\Parameters
    • Application = "%System%\boorcservice.exe"

Step 5

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 Temp%\E_4\krnln.fnr
  • %User Temp%\E_4\Exmlrpc.fne
  • %User Temp%\E_4\dp1.fne
  • %System%\boorcservice.exe
  • %System Root%\del_file_b.bat
  • %System%\boorcservice.dll
  • %User Temp%\_eviip.tmp
  • %User Temp%\e_4\boordc7ac.dll
  • %Windows%\Fonts\09e84031a107f84a8d2ad6cdfb3b06b5.dat
  • %User Temp%\E_4\krnln.fne

Step 6

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.
  • %User Temp%\E_4

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_FLYSTUDI.AN. 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 8

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.

  • %System Root%\DEL_FI~1.BAT


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