TROJ_DNSCHANG.YI
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Trojan
Destructiveness: No
Encrypted: Yes
In the wild: Yes
OVERVIEW
It changes the TCP Port of Internet Information Services (IIS) of the affected system to a new random number. The new port number will be saved by the malware in a certain registry.
This Trojan may be downloaded by other malware/grayware/spyware from remote sites. It may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.
It connects to certain URLs. It may do this to remotely inform a malicious user of its installation. It may also do this to download possibly malicious files onto the computer, which puts the computer at a greater risk of infection by other threats.
TECHNICAL DETAILS
Arrival Details
This Trojan may be downloaded by other malware/grayware/spyware from remote sites.
It may be dropped by other malware.
It may be unknowingly downloaded by a user while visiting malicious websites.
Installation
This Trojan drops the following file(s)/component(s):
- %System%\spool\driver\PMTP_TEMP_CONFIG.INI
(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.)
It drops the following copies of itself into the affected system:
- %System%\spool\drivers\nps.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.)
Autostart Technique
This Trojan registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network Port Services
Type = 10
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network Port Services
Start = 2
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network Port Services
ErrorControl = 1
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network Port Services
ImagePath = %System%\spool\drivers\nps.exe /Start
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network Port Services
DisplayName = Network Port Services
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network Port Services
ObjectName = LocalSystem
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network Port Services
Description = This Service analysis Network Ports. If this service was stopped, the computer will not be able to resolve Network Port and location Active Directory domain controller. If this service is disabled, any clear rely on its services will not be able to start.
Other System Modifications
This Trojan adds the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService_Temp
It adds the following registry entries as part of its installation routine:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService
Service = Network Port Services
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService
Programe = nps.exe
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService
Description = This Service analysis Network Ports. If this service was stopped, the computer will not be able to resolve Network Port and location Active Directory domain controller. If this service is disabled, any clear rely on its services will not be able to start.
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService
ClientID = Ours
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService
FirstServer = http://www.highest-developments.com/ptmp2.php
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService
SecondServer = http://www.moderinnovation.com/ptmp2.php
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService
ThirdServer = http://www.spf-domainkey.com/ptmp2.php
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService
Disallow = bl.php
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService
DomainVer = du.txt
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService
DomainList = dd.txt
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
PTMPService
IISPort = {new IIS Port number}
It creates the following registry entry(ies) to bypass Windows Firewall:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile\AuthorizedApplications\
List
BW-PTMP = %System%\spool\drivers\nps.exe:*:enabled:Explorer
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
BW-PTMP = %System%\spool\drivers\nps.exe:*:enabled:Explorer
Download Routine
This Trojan connects to the following malicious URLs:
- http://www.{BLOCKED}t-developments.com/ptmp2.php
- http://www.{BLOCKED}nnovation.com/ptmp2.php
- http://www.{BLOCKED}mainkey.com/ptmp2.php
Other Details
This Trojan does the following:
- Changes the TCP Port of Internet Information Services (IIS) of the affected system to a new random number. The new port number will be saved by the malware in the following registry:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PTMPService
IISPort = {new IIS Port value}
SOLUTION
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
Step 3
Delete this registry key
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
- Network Port Services
- Network Port Services
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft
- PTMPService
- PTMPService
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft
- PTMPService_Temp
- PTMPService_Temp
Step 4
Delete this registry value
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\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
- BW-PTMP = %System%\spool\drivers\nps.exe:*:enabled:Explorer
- BW-PTMP = %System%\spool\drivers\nps.exe:*:enabled:Explorer
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
- BW-PTMP = %System%\spool\drivers\nps.exe:*:enabled:Explorer
- BW-PTMP = %System%\spool\drivers\nps.exe:*:enabled:Explorer
Step 5
Search and delete these files
- %System%\spool\driver\PMTP_TEMP_CONFIG.INI
Please visit the following link for instruction on how to change the TCP Port for IIS services.
Step 6
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DNSCHANG.YI. 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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