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 adds certain registry entries to disable the Task Manager. This action prevents users from terminating the malware process, which can usually be done via the Task Manager.
It deletes the initially executed copy of itself.
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 drops the following copies of itself into the affected system:
- %Application Data%\{Random File Name}.exe
(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)
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
{Random Name} = "%Application Data%\{Random File Name}.exe"
Other System Modifications
This Trojan adds the following registry entries as part of its installation routine:
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Download
CheckExeSignatures = "no"
(Note: The default value data of the said registry entry is "yes".)
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Attachments
SaveZoneInformation = 1
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Associations
LowRiskFileTypes = ".zip;.rar;.nfo;.txt;.exe;.bat;.com;.cmd;.reg;.msi;.htm;.html;.gif;.bmp;.jpg;.avi;.mpg;.mpeg;.mov;.mp3;.m3u;.wav;.scr;"
It adds the following registry entries to disable the Task Manager:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = 1
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
DisableTaskMgr = 1
Other Details
This Trojan deletes the initially executed copy of itself
Rogue Antivirus Routine
This Trojan displays the following fake alerts:
- Failed to read system files configuration. Start a system diagnostics application to scan your hard disk for errors and performance problems.
- A performance problem with one or more installed IDE / SATA hard drives has been detected. System restart is highly recommended.
- Un error ocurrio durante la lectura de los ficheros del sistema. Ejecute la utilidad diagnostica del sistema para chequear su unidad del disco duro para errores.
- El sistema ha detectado un problema con uno o mas IDE / SATA discos duros instalados. Vd. esta aconsejado a reiniciar el sistema.
- Ein Fehler beim Lesen Systemdateien eingetreten. Fuhren Sie ein Diagnoseprogramm fur Fehlerbestimmung durch.
- Das System hat ein Problem mit einem oder mehreren installierten IDE / SATA-Festplatten erkannt. Es wird empfohlen, das System neu zu starten.
- Errore durante la lettura di file di sistema Lanciate l'utilita di diagnostica del sistema per verificare il hard disk per gli errori.
- Il sistema ha rilevato un problema con uno o pi? hard disk IDE / SATA istallati. Si raccomanda di riaccendere il sistema.
- utilitaire de diagnostique du systeme pour detecter les erreurs sur votre disque dur.
- Le systeme a detecte un probleme avec un ou plusieurs disques durs IDE / SATA installes. Nous vous recommandons de redemarrer votre systeme.
- Sistem dosyalar? okuma s?ras?nda hata olusmustur. Sistem tan?mlama yard?mc? program?n? sabit disk surucusunu kontrol etmek icin baslay?n.
- Sistem yuklenmis bir veya fazlas? olan IDE / SATA sabit disklerde hatay? tespit etti. Sisteminizi yeniden baslatman?z tavsiye edilir.
NOTES:
This Trojan may perform the following routines:
- Show defrag window
- Download and saves a file from a URL
- Change wallpapper
- Display dialog boxes
- Hide files
- Terminate/delete itself
- Show balloon messages in the system tray
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
Scan your computer with your Trend Micro product and note files detected as TROJ_KRYPTK.SMUF
Step 3
Restart in Safe Mode
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To restart in Safe Mode:
• For Windows 2000 users
- Restart your computer.
- Press F8 when you see the Starting Windows bar at the bottom of the screen.
- Choose the Safe Mode option from the Windows Advanced Options menu then press Enter.
• For Windows XP users
- Restart your computer.
- Press F8 after the Power-On Self Test (POST) routine is done. If the Windows Advanced Options menu does not appear, try restarting then pressing F8 several times when the POST screen appears.
- Choose the Safe Mode option from the Windows Advanced Options menu then press Enter.
• For Windows Server 2003 users
- Restart your computer.
- Press F8 after Windows starts up. If the Windows Advanced Options menu does not appear, try restarting again and pressing F8 several times afterward.
- On the Windows Advanced Option menu, use the arrow keys to select Safe Mode then press Enter.
Step 4
Delete this registry value
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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
- {Random Name} = "%Application Data%\{Random File Name}.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Associations
- LowRiskFileTypes = ".zip;.rar;.nfo;.txt;.exe;.bat;.com;.cmd;.reg;.msi;.htm;.html;.gif;.bmp;.jpg;.avi;.mpg;.mpeg;.mov;.mp3;.m3u;.wav;.scr;"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Attachments
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system
To delete the registry value this malware created:
- Open Registry Editor. To do this, click Start>Run, type regedit in the text box provided, then press Enter.
- In the left panel of the Registry Editor window, double-click the following:
HKEY_CURRENT_USER>Software>Microsoft>Windows>CurrentVersion>Run - In the right panel, locate and delete the entry:
{Random Name} = "%Application Data%\{Random File Name}.exe" - In the left panel of the Registry Editor window, double-click the following:
HKEY_CURRENT_USER>Software>Microsoft>Windows>CurrentVersion>Policies>Associations - In the right panel, locate and delete the entry:
LowRiskFileTypes = ".zip;.rar;.nfo;.txt;.exe;.bat;.com;.cmd;.reg;.msi;.htm;.html;.gif;.bmp;.jpg;.avi;.mpg;.mpeg;.mov;.mp3;.m3u;.wav;.scr;" - In the left panel of the Registry Editor window, double-click the following:
HKEY_CURRENT_USER>Software>Microsoft>Windows>CurrentVersion>Policies>Attachments - In the right panel, locate and delete the entry:
SaveZoneInformation = 1 - In the left panel of the Registry Editor window, double-click the following:
HKEY_CURRENT_USER>Software>Microsoft>Windows>CurrentVersion>Policies>System - In the right panel, locate and delete the entry:
DisableTaskMgr = 1 - In the left panel of the Registry Editor window, double-click the following:
HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows>CurrentVersion>policies>system - In the right panel, locate and delete the entry:
DisableTaskMgr = 1 - Close Registry Editor.
Step 5
Restore this modified registry value
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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\Download
- From: CheckExeSignatures = "no"
To: "yes"
To restore the registry value this malware/grayware/spyware modified:
- Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
- In the left panel, double-click the following:
HKEY_CURRENT_USER>Software>Microsoft>Internet Explorer>Download - In the right panel, locate the registry value:
CheckExeSignatures = "no" - Right-click on the value name and choose Modify. Change the value data of this entry to:
CheckExeSignatures = "yes" - Close Registry Editor.
Step 6
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_KRYPTK.SMUF. 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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