Threat Encyclopedia

Description: 

This Trojan arrives on a system as a downloaded file from the Internet by unsuspecting users when visiting malicious Web sites. It may also arrive as a dropped file of TROJ_MDROPPER.AW or other malware.

It connects to certain URLs to download and execute possibly malicious files, which, in turn, can connect to other Web sites to download files.

It drops copies of itself using the file names SHSTAT.EXE and SKADEMON.EXE in the Windows system folder.

Details:

This Trojan arrives on a system as a downloaded file from the Internet by unsuspecting users when visiting malicious Web sites. It may also arrive as a dropped file of TROJ_MDROPPER.AW or other malware.

It drops copies of itself using the following file names in the Windows system folder:

• SHSTAT.exe
• SKADEmon.exe

It modifies the following registry entry to execute at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "%System%\userinit.exe,%System%\SHSTAT.exe"

(Note: %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. The default value of the said entry is Userinit = "%System%\userinit.exe". On NT-based systems, the corresponding default value is %system%\userinit.exe, {nddeagnt.exe}".)

It connects to the following URLs to download and execute possibly malicious files, which, in turn, can connect to other Web sites to download files:

• http://broadcom.di{BLOCKED}yserver.net/cgi-bin/Owpq4.cgi
• http://broadcom.di{BLOCKED}yserver.net/cgi-bin/Clnpp5.cgi
• http://broadcom.di{BLOCKED}yserver.net/cgi-bin/Crpq2.cgi
• http://broadcom.di{BLOCKED}yserver.net/cgi-bin/Dwpq3.cgi
• http://broadcom.di{BLOCKED}yserver.net/cgi-bin/Rwpq1.cgi
• http://broadcom.di{BLOCKED}yserver.net/httpdocs/mm/{User name}:
  {random code}/Cmwhite
• http://broadcom.di{BLOCKED}yserver.net/httpdocs/mm/{User name}:
  {random code}/Tiblue

(Note: {User name} is the computer name or user name of the current user. {random code} refers to a certain code that this Trojan generates.)

This Trojan runs on Windows 98, ME, NT, 2000, XP, and Server 2003.

Analysis By: Jonathan N. San Jose

Important note: The "Minimum scan engine" refers to the earliest Trend Micro scan engine version guaranteed to detect this threat. However, Trend Micro strongly recommends that you update to the latest version in order to get comprehensive protection. Download the latest scan engine here.

Solution:

Note: To fully remove the associated malware, perform the clean solution for TROJ_MDROPPER.AW.

Identifying the Malware Program

To remove this malware, first identify the malware program.

1. Scan your computer with your Trend Micro antivirus product.
2. NOTE the path and file name of all files detected as TROJ_SHARP.R.

Trend Micro customers need to download the latest virus pattern file before scanning their computer. Other users can use Housecall, the Trend Micro online virus scanner.

Terminating the Malware Program

This procedure terminates the running malware process. You will need the name(s) of the file(s) detected earlier.

If the process you are looking for is not in the list displayed by Task Manager, proceed to the succeeding solution set.

1. Open Windows Task Manager.
   • On Windows 98 and ME, press
   CTRL+ALT+DELETE
   • On Windows NT, 2000, XP, and Server 2003, press
   CTRL+SHIFT+ESC, then click the Processes tab.
2. In the list of running programs*, locate the malware file(s) detected earlier.
3. Select one of the detected files, then press either the End Task or the End Process button, depending on the version of Windows on your computer.
4. Do the same for all detected malware files in the list of running processes.
5. To check if the malware process has been terminated, close Task Manager, and then open it again.
6. Close Task Manager.

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*NOTE: On computers running Windows 98 and ME, Windows Task Manager may not show certain processes. You can use a third party process viewer such as Process Explorer to terminate the malware process.

On computers running all Windows platforms, if the process you are looking for is not in the list displayed by Task Manager or Process Explorer, continue with the next solution procedure, noting additional instructions. If the malware process is in the list displayed by either Task Manager or Process Explorer, but you are unable to terminate it, restart your computer in safe mode.

Editing the Registry

This malware modifies the computer's registry. Users affected by this malware may need to modify or delete specific registry keys or entries. For detailed information regarding registry editing, please refer to the following articles from Microsoft:

1. HOW TO: Backup, Edit, and Restore the Registry in Windows 95, Windows 98, and Windows ME
2. HOW TO: Backup, Edit, and Restore the Registry in Windows NT 4.0
3. HOW TO: Backup, Edit, and Restore the Registry in Windows 2000
4. HOW TO: Back Up, Edit, and Restore the Registry in Windows XP and Server 2003

Restoring Modified Autostart Enty in the Registry

Restoring modified autostart entry from the registry prevents the malware from executing at startup.

If the registry entry below is not found, the malware may not have executed as of detection. If so, proceed to the succeeding solution set.

1. Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
2. In the left panel, double-click the following:
   HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>
   Windows NT>CurrentVersion>Winlogon
3. In the right panel, locate the entry:
   Userinit = "%System%\userinit.exe,%System%\SHSTAT.exe"
   (Note: %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, and C:\Windows\System32 on Windows XP and Server 2003.)
4. Right-click on this registry entry and choose Modify. Change the value of this entry to:
   Userinit = "%System%\userinit.exe"

(Note: On NT-based systems, the corresponding default value is
Userinit = "%System%\userinit.exe, {nddeagnt.exe}".)
5. Close Registry Editor.

Important Windows ME/XP Cleaning Instructions

Users running Windows ME and XP must disable System Restore to allow full scanning of infected computers.

Users running other Windows versions can proceed with the succeeding solution set(s).

Running Trend Micro Antivirus

If you are currently running in safe mode, please restart your computer normally before performing the following solution.

Scan your computer with Trend Micro antivirus and delete files detected as TROJ_SHARP.R. To do this, Trend Micro customers must download the latest virus pattern file and scan their computer. Other Internet users can use HouseCall, the Trend Micro online virus scanner.

Trend Micro offers best-of-breed antivirus and content-security solutions for your corporate network, small and medium business, mobile device or home PC.