ALIASES:

Trojan:Win32/Punad.C (Microsoft); Downloader (Symantec); PAK:Execryptor, Trojan-Clicker.Win32.VBiframe.zu (Kaspersky); Trojan.Win32.Generic.pak!cobra (Sunbelt); MemScan:Trojan.Clicker.MUC (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • 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: 164,818 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 15 Oct 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\
Windows\CurrentVersion\Run
net = "%System%\net.net"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
net

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
net
DisplayName = "Advertisement Service"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
net
DisplayVersion = "1.0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
net
UninstallString = "%System%\net.net Uninstall"

It deletes the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\clicksor.com\
creative

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\clicksor.com\
ads

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\clicksor.com

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\clicksor.net\
serving.adsrevenue

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\clicksor.net

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\adsrevenue.net\
popunder

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
ZoneMap\Domains\adsrevenue.net

Dropping Routine

This Trojan drops the following files:

  • %System%\net.net

(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.)

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\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall
    • net

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\Windows\CurrentVersion\Run
    • net = "%System%\net.net"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\net
    • DisplayName = "Advertisement Service"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\net
    • DisplayVersion = "1.0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\net
    • UninstallString = "%System%\net.net Uninstall"

Step 5

Search and delete this file

[ 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.
  • %System%\net.net

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_CLICKER.COB. 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 7

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\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains\clicksor.com
    • creative
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains\clicksor.com
    • ads
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains
    • clicksor.com
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains\clicksor.net
    • serving.adsrevenue
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains
    • clicksor.net
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains\adsrevenue.net
    • popunder
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains
    • adsrevenue.net


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