Infostealer.Tarno.S

There are two distinct components to this Trojan, a downloader component and a main component.

The downloader component of this Trojan is reported to arrive on the compromised computer as an attachment to an email message from the PayPal Account Review Department.

Once the attachment to this message is opened, the main component of this Trojan is downloaded as the following file:

[http://]akgulati.com/suho[REMOVED]

The downloader component then adds the value:

"[PATH TO THE DOWNLOADER COMPONENT]" = "[PATH TO THE DOWNLOADER COMPONENT]:*:enabled:B"

to the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ServiceS\Sharedaccess\parameters
\Firewallpolicy\StandardProfile\AuthorizedApplications\List

in order to bypass the Windows Connection Firewall by adding itself to the authorized list.

Once the main component of Infostealer.Tarno.S is executed, it performs the following actions:

1. Creates the following files:
   
   
   • %System%\guisetup.exe
   • %System%\msupdate.dll
     
     Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).
     
     
2. Registers the file %System%\msupdate.dll as a Browser Helper Object, which runs every time Internet Explorer starts. In registering this file, the Trojan creates registry entries under the following registry subkeys:
   
   HKEY_CLASSES_ROOT\CLSID\{3A4E6FF3-BF59-446E-9DC8-731BCE2F349A}
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects\{3A4E6FF3-BF59-446E-9DC8-731BCE2F349A}
   
   
3. Registers itself by creating the following registry subkey:
   
   HKEY_CLASSES_ROOT\msupdate.MSIE Update Service
   
   
4. Monitors windows and Web pages that contain the following strings, in an attempt to target user name and password data related to Internet banking activities:
   
   
   • gold
   • cash
   • bank
   • pas
   • log
   • user
   • usr
   • pwd
   • psw
   • pw
   • parol
   • firma
   • pin
   • clave
   • trans
   • porcue
   • memorable
   • secret
   • id
     
     
5. Captures keystrokes entered into any windows it finds. It also logs HTML Web forms transferred from the compromised computer to any remote Web sites visited, once an active window exists.
   
   
6. Logs the information it gathers into some of the following files:
   
   
   • %System%\wint.ini
   • %System%\ierror.rep
   • %System%\sui.dll
   • %System%\sei.dll
     
     
7. Creates the following file:
   
   %System%\winte.html
   
   
8. Creates the following folders which may be used to store configuration files or extensions for this Trojan:
   
   
   • %System%\suskn
   • %System%\sucontr
   • %System%\suact
     
     
9. Constructs the following HTTP GET request, in order to send a unique ID of the compromised computer to a remote attacker:
   
   [http://]lifedarts.com/arhi/naviga[REMOVED]
   
   
10. Periodically sends any information it gathers to the following URL:
    
    [http://]lifedarts.com/arhi/report[REMOVED]

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
• Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
• Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
• Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
• Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
• Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
• If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
• Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
• Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
• If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
• For further information on the terms used in this document, please refer to the Security Response glossary.

Summary