Backdoor.Amitis

SUMMARY

The Backdoor.Amitis Backdoor Trojan gives an attacker unauthorized access to an infected computer. By default, the Trojan opens TCP port 27,551 on the infected computer. This threat is written in Microsoft Visual Basic, version 6.

Protection

• Virus Definitions (LiveUpdate™ Weekly) January 8, 2003
• Virus Definitions (Intelligent Updater) January 7, 2003

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: Medium
• Compromises Security Settings: gives an attacker unauthorized access to an infected computer.

Distribution

• Distribution Level: Low
• Ports: 27,551

TECHNICAL DETAILS

When Backdoor.Amitis runs, it does the following:

1. Copies itself to the %Windir% folder. The file name is not fixed, and the name of the copied file name is the same as the one you executed. For example, if the Trojan file name is Server.scr, it copies itself as %Windir%Server.scr, when you run Server.scr.
   
   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. If the operating system is Windows 95/98/Me, the Trojan may add a reference to itself to the Run= and load= lines in the [windows] section of the Win.ini file. For example:
   
   [windows]
   run=%windir%<file name of Trojan>
   load==%windir%<file name of Trojan>
   
   so that the Trojan starts each time you start Windows.
   
3. On Windows NT/2000/XP, the Trojan adds the value:
   
   load %windir%<file name of Trojan>open=%windir%<filename>
   
   to the registry keys:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersionWindows
   HKEY_USER<User ID>SoftwareMicrosoftWindows NTCurrentVersionWindows
   
   Because this command is not correctly formatted, the Trojan does not start when you start Windows on these operating systems.
   
4. Opens TCP port 27,551 to wait for a connection from the hacker.

Recommendations

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

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended 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 (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. 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.

REMOVAL

These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Update the virus definitions.
2. Run a full system scan and delete all the files detected as Backdoor.Amitis.
3. Edit the files. Do one of the following:
   • Windows 95/98/Me: Edit the Win.ini file and remove the text that the Backdoor Trojan added to the run= and load= lines.
   • Windows NT/2000/XP: Edit the registry and remove the lines that the Backdoor Trojan added to the Run key.
     

For details on each of these procedures, read the following instructions.

1. Updating the virus definitions

Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:

• Running LiveUpdate, which is the easiest way to obtain the virus definitions. These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate), in the "Protection" section, at the top of this writeup.
• Downloading the definitions using the Intelligent Updater. The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater), in the "Protection" section, at the top of this writeup.

The Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

2. Scanning for and deleting the infected files detected as Backdoor.Amitis

1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
   • For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
   • For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan All Files."
2. Run a full system scan.
3. If any files are detected as infected with Backdoor.Amitis, click Delete.

3. Editing the files

Do one of the following:

• Windows 95/98/Me: Edit the Win.ini file and remove the text that the Backdoor Trojan added to the run= and load= lines.
• Windows NT/2000/XP: Edit the registry and remove the lines that the Backdoor Trojan added to the Run key.

For detailed information on editing files, read the following instructions.

Editing the Win.ini file
This is necessary only if you are running Windows 95/98/Me.

NOTE for Windows Me users only: Due to the file-protection process in Windows Me, a backup copy of the file you are to edit exists in the C:WindowsRecent folder. Symantec recommends that you delete this file before you continue with the steps in this section. To do this using Windows Explorer, go to C:WindowsRecent, and in the right pane select the Win.ini file and delete it. It will be regenerated as a copy of the file you are to edit, when you save your changes to that particular file.

1. Click Start, and then click Run.
2. Type the following, and then click OK.
   
   edit c:windowswin.ini
   
   (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
3. In the [windows] section of the file, look for an entry similar to:
   
   load=%windir%<file name of Trojan>
   
4. Select the entire line. Be sure that you have not selected any other text, and then press Delete.
5. In the [windows] section of the file, look for a line similar to:
   
   run=%windir%<file name of Trojan>
   
6. If it exists, select the entire line. Be sure that you do not select any other text, and then press Delete.
7. Click File, and then click Save.
8. Click File, and then click Exit.

Editing the registry
This is necessary only if you are running Windows NT/2000/XP.

CAUTION: Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to make a backup of the Windows registry," for instructions.

1. Click Start, and then click Run. (The Run dialog box appears.)
2. Type regedit, and then click OK. (The Registry Editor opens.)
3. Navigate to the key:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersionWindows
   
4. In the right pane, delete the value:
   
   load %windir%<file name of Trojan>open=%windir%<filename>
   
5. Navigate to the key:
   
   HKEY_USER<User ID>SoftwareMicrosoftWindows NTCurrentVersionWindows
   
6. In the right pane, delete the value:
   
   load %windir%<file name of Trojan>open=%windir%<filename>
   
7. Exit the Registry Editor.