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TROJ_AGENT
Malware type: Trojan
Destructive: No
Platform: Windows 2000, Windows XP, Windows Server 2003
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.

Technical Details


File size: 1,702,893 bytes
File type: EXE
Memory resident: Yes
Initial samples received date: 07 Jun 2012

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.

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{5BC31741-73A1-4f37-8965-0E50520FAFAD}
stubpath = "%System%\inortslka.exe"

It 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\PCRatStact

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{5BC31741-73A1-4f37-8965-0E50520FAFAD}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\PCRatStact
Type = "12"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\Session Manager\SFC
ProgramFilesDir = "%Program Files%"

(Note: The default value data of the said registry entry is %Program Files%.)

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\Session Manager\SFC
CommonFilesDir = "%Program Files%\Common Files"

(Note: The default value data of the said registry entry is %Program Files%\Common Files.)

It deletes the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Active Setup\Installed Components\{5BC31741-73A1-4f37-8965-0E50520FAFAD}

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\server.exe
  • %User Temp%\¸ÅÅ©·Î.exe
  • %System%\inortslka.exe
  • %System%\syslog.dat
  • %User Temp%\41015_res.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.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

This report is generated via an automated analysis system.

Solution


Minimum scan engine: 9.200

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

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
    • PCRatStact
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {5BC31741-73A1-4f37-8965-0E50520FAFAD}

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\Active Setup\Installed Components\{5BC31741-73A1-4f37-8965-0E50520FAFAD}
    • stubpath = "%System%\inortslka.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\PCRatStact
    • Type = "12"

Step 5

Restore this modified 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\Control\Session Manager\SFC
    • From: ProgramFilesDir = "%Program Files%"
      To: ProgramFilesDir = ""%Program Files%""
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\SFC
    • From: CommonFilesDir = "%Program Files%\Common Files"
      To: CommonFilesDir = ""%Program Files%\Common Files""

Step 6

Search and delete these files

[ Learn more ]
There may be some component files 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%\server.exe
  • %User Temp%\¸ÅÅ©·Î.exe
  • %System%\inortslka.exe
  • %System%\syslog.dat
  • %User Temp%\41015_res.tmp

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_AGENT. 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 these deleted registry keys/values from backup

*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.


  • In HKEY_CURRENT_USER\Software\Microsoft\Active Setup\Installed Components
    • {5BC31741-73A1-4f37-8965-0E50520FAFAD}


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Analysis By: Automation

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