Backdoor.Hale

SUMMARY

Backdoor.Hale is a package of programs that provide backdoor access to an infected computer. This threat includes a Backdoor Trojan detected as Backdoor.Padmin, an FTP server, and various system utilities.

The existence of a C:WinntSystem32Qossrv folder is an indication of a possible infection. Some variants use C:WinntSystem32Dhcp instead, but this folder may be present on uninfected computers.

There have been reports that this threat is distributed by exploiting the DCOM RPC vulnerability, described in Microsoft Security Bulletin MS03-026. University domains have been heavily targeted.

Protection

• Virus Definitions (LiveUpdate™ Weekly) August 6, 2003
• Virus Definitions (Intelligent Updater) August 6, 2003

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 3 - 9
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: Medium
• Payload: Installs a Backdoor Trojan Horse and an FTP server.
• Compromises Security Settings: Allows unauthorized remote access to an infected computer.

Distribution

• Distribution Level: Low
• Ports: 6351, 5555, 48522

TECHNICAL DETAILS

NOTE: Symantec Security Response has received several variants of this backdoor package. Two such variants are described below, but other variants could appear that use different filenames and directories.

Version 1

The installer for this version is a self-extracting CAB archive. It may be found in the system folder as a file named Nx.exe.

When Backdoor.Hale is executed, it performs the following actions:

1. Creates the folder, C:WinntSystem32Qossrv.
   
   NOTE: This path is hard-coded and is used for all the operating systems.
   
   
2. Copies the following files into the above directory:
   
   • Aysshell.exe: A legitimate "At Your Service" utility from Prism Microsystems.
   • Cdir.txt: A harmless text file.
   • Csrss.exe: a Backdoor Trojan Horse detected as Backdoor.Padmin.
   • Firedaemon.exe: A legitimate FireDaemon utility (used to start service processes).
   • Libeay32.dll: A legitimate .dll file.
   • Mswinsck.ocx: A legitimate .ocx file.
   • Pskill.exe: A legitimate utility used to kill processes.
   • Secure.exe: Detected as Backdoor.Hale.
   • Servuperfcount.dll: A legitimate .dll file that Winmgnt.exe uses.
   • Setup.bat: A batch file detected as Backdoor.Hale.
   • Setup.pif: A harmless .pif file.
   • Ssleay.dll: A legitimate .dll file.
   • Winmgnt.exe: a Serv-U FTP server.
   • Winexplorer.dll: This is not a .dll, but a configuration file for the FTP server.
   • Wget.exe: A legitimate program to fetch files using HTTP.
   • "- V1.0D (Haley) -": A 0-byte file.
     
     
3. Adds the value:
   
   "NTDLM" = "c:winntsystem32qossrvcsrss.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   
4. Adds the value:
   
   "port" = "6351"
   
   to the registry key:
   
   HKEY_CURRENT_USERSoftwareVB and VBA Program SettingspAdminSettings
   
   to open port 6351.
   
   
5. Removes the network shares listed on the computer.
   
   
6. Uses Asyshell.exe to start the following services:
   
   • NTF (Winmgnt.exe)
   • NTS (Secure.exe)
   • NTP (Csrss.exe)
     
     NOTE: Some variants may use different names for the services.
     
     
7. Opens ports 5555 and 48522 using Winmgnt.exe.

Version 2:

This variant is not known to use a self-contained installer, like Nx.exe in the previous version.

The infection is similar to Version 1, except the files are copied into these directories:

C:WinntSystem32dhcp:

• Csrsslsrms.dll: A text file, not a dll.
• Explorer.exe: A Serv-U FTP server, detected as Backdoor.Hale.
• Fport.exe: A utility used to list the processes with open network connections.
• Igfxtray.exe: Detected as Backdoor.Trojan.
• Nc.exe: A network utility.
• Ntlmconf.dll: A text file, not a dll.
• Pskill.exe: A utility used to kill processes.
• Pslist.exe: A utility used to list processes.
• Rar.exe: An archive utility.
• Reg.exe: A utility used to edit the registry.
• Rmns.exe: Detected as Backdoor.Hale.
• Service.exe: A utility used to start the service processes.
• SystemUptimeLog.ocx: A log file.
• Tar.exe: An archive utility.
• Tlister.exe: A utility used to list processes.
• Wget.exe: A utility used to fetch files using HTTP.
• WinExplorer.dll: A configuration file, not a dll.

C:WinntSystem32estore:

• Csrss.exe: Detected as Backdoor.Padmin.
• MSWINSCK.OCX: A legitimate system file.
• Pskill.exe: A utility used to kill processes.
• Reg.exe: A utility used to edit the registry.
• Service.exe: A utility used to start the service processes.
• Binary.gif
• Compressed.gif
• Del.gif
• Dir.gif
• Folder.open.gif
• Image1.gif
• Image2.gif
• Movie.gif
• Pdf.gif
• Script.gif
• Sound2.gif
• Tar.gif
• Text.gif
• Thumbs.db

There have also been reports of variants that install files in C:WinntSystem32config or C:WinntSystem32home; and other folder and file names may be used in the future.

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

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Disable System Restore (Windows Me/XP).
2. Update the virus definitions.
3. Restart the computer in Safe mode or VGA mode.
4. Run a full system scan and delete all the files detected as Backdoor.Padmin, Backdoor.Hale, or Backdoor.Trojan. Delete the C:winntsystem32qossrv directory and its contents, or other files listed in the "Technical Details" section.
5. Delete the values that were added to the registry.
   

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

1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:

• "How to disable or enable Windows Me System Restore"
• "How to turn off or turn on Windows XP System Restore"

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder," Article ID: Q263455.

2. 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 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).
• 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).
  
  The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. Restarting the computer in Safe mode or VGA mode

• For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, refer to the document, "How to start the computer in Safe Mode."
• For Windows NT 4 users, restart the computer in VGA mode.

4. Scanning for and deleting the infected files

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.Hale or Backdoor.Padmin, click Delete.
4. Using Windows Explorer, delete the directory, C:winntsystem32qossrv or C:winntsystem32estore. Delete any files in C:winntsystem32dhcp, listed in the "Technical Details" section.

5. Deleting the values from the registry

CAUTION: Symantec strongly recommends that you back up the registry before making 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
   Then click OK. (The Registry Editor opens.)
   
   
3. Navigate to the key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
4. In the right pane, delete any value which refers to the backdoor files, for instance:
   
   "NTDLM"="c:winntsystem32qossrvcsrss.exe"
   
   
5. Navigate to the key:
   
   HKEY_CURRENT_USERSoftwareVB and VBA Program SettingspAdminSettings
   
   
6. In the right pane, delete the value:
   
   "port"="6351"
   
   
7. Exit the Registry Editor.