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TSPY_FLYSTUD.BI

June 30, 2013
 ALIASES:

Worm:Win32/Nuj.A (Microsoft); [2.nsis]:BackDoor-DPR (McAfee); Trojan Horse (Symantec); ARC:NSIS, ARC:[1.exe]:Embedded, [1.exe/script.fly]:Trojan-Dropper.Win32.Flystud.ah, PAK:[1.exe/krnln (Kaspersky); BehavesLike.Win32.Malware.bsf (vs) (Sunbelt); Trojan:W32/Agent.DQRS (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 REPORTED INFECTION:
 SYSTEM IMPACT RATING:
 INFORMATION EXPOSURE:

  • Threat Type: Spyware

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This spyware 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:

1,168,358 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Apr 2012

Arrival Details

This spyware 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 spyware creates the following folders:

  • %System Root%\DOCUME~1
  • %System Root%\DOCUME~1\ADMINI~1
  • %User Profile%\LOCALS~1
  • %User Temp%\nsd2.tmp
  • %User Temp%\E_4

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

Other System Modifications

This spyware deletes the following files:

  • %User Temp%\nsx1.tmp
  • %User Temp%\nsd2.tmp

(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.)

It adds the following registry entries:

HKEY_CURRENT_USER\Software
ifile = "{malware path and file name}%xy2.eif"

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

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Prstgressep\Parameters
Application = "%System%\PrstService.exe"

Dropping Routine

This spyware drops the following files:

  • %User Temp%\1.exe
  • %User Temp%\xy2.eif
  • %User Temp%\nsd2.tmp\System.dll
  • %User Temp%\E_4\krnln.fnr
  • %User Temp%\E_4\dp1.fne
  • %User Temp%\E_4\Exmlrpc.fne
  • %System Root%\delus.bat
  • %System%\PrstService.dll
  • %User Temp%\_EVLPK.tmp
  • %Program Files%\Internet Explorer\IJL105.DLL
  • eif
  • %System%\PrstService.exe
  • %Windows%\Fonts\PrstService.jpg
  • %Program Files%\Internet Explorer\dp1.fne
  • %Program Files%\Internet Explorer\Exmlrpc.fne
  • %Program Files%\Internet Explorer\krnln.fnr

(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 Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %System% is the Windows system folder, which is usually C:\Windows\System32.. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).. %Windows% is the Windows folder, which is usually C:\Windows.)

Other Details

This spyware deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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\Prstgressep
    • Parameters

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
    • ifile = "{malware path and file name}%xy2.eif"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • Check_Associations = "NO"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Prstgressep\Parameters
    • Application = "%System%\PrstService.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%\1.exe
  • %User Temp%\xy2.eif
  • %User Temp%\nsd2.tmp\System.dll
  • %User Temp%\E_4\krnln.fnr
  • %User Temp%\E_4\dp1.fne
  • %User Temp%\E_4\Exmlrpc.fne
  • %System Root%\delus.bat
  • %System%\PrstService.dll
  • %User Temp%\_EVLPK.tmp
  • %Program Files%\Internet Explorer\IJL105.DLL
  • eif
  • %System%\PrstService.exe
  • %Windows%\Fonts\PrstService.jpg
  • %Program Files%\Internet Explorer\dp1.fne
  • %Program Files%\Internet Explorer\Exmlrpc.fne
  • %Program Files%\Internet Explorer\krnln.fnr

Step 6

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.
  • %System Root%\DOCUME~1
  • %System Root%\DOCUME~1\ADMINI~1
  • %User Profile%\LOCALS~1
  • %User Temp%\nsd2.tmp
  • %User Temp%\E_4

Step 7

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

  • %User Temp%\nsx1.tmp
  • %User Temp%\nsd2.tmp


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