Downloader.Inor.B

When Downloader.Inor.B is executed, it performs the following actions:

1. Drops the file %Windir%\System32\Usb_d2.exe, and then executes it.
   
   

   ---

   Note: %Windir% is a variable. The Trojan locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.

   ---

   
   
2. Opens a random TCP port and starts a proxy service.
   
   
3. Sends the port number of the local proxy to a listening server every 30 seconds. The URL of the server is in a format similar to http://<domain>/sd/<port number>
   
   
4. Attempts to add the value:
   
   "UsbD"="usb_d2.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   
   so that the Trojan runs when you start Windows.
   
   
5. Attempts to download a file from a predetermined Web site. The file that it tries to download may vary.

Sample email messages
The following two email samples were used to spread this Trojan:

Subject: Virus Alert
To:<user>
From: <company name> Internet Virus Department
Message:
We have detected a possible computer virus on your computer, You must open the details of the report within 24 hours our we will be forced to shut down your internet service.

Please Click Below Then Press "open" To View The Report If you do not open this report in 24 hours we will suspend your internet service If nothing apears on your virus report please dis-regard this message
Click Here Now
<URL>


Subject: "Billing Notice From <company name>'s Accounting Dpt"
Attachment: Page.hta
Message:
***  <company name>'s accounting dpt notice ***
Internet Billing Notice
Please press "open" and read the attached Billing Notice.

Note if you do not read this withing 24 hours we at <company name> regret we will have to terminate internet service

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