Backdoor.EggHead

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Discovered: February 11, 2002
Updated: February 13, 2007 11:46:24 AM
Type: Trojan Horse


Backdoor.EggHead is a backdoor Trojan horse program that uses a freeware IRC bot as its core component.

This backdoor works only under Windows NT/2000/XP.

Once activated, this backdoor gives a third party unrestricted access to the client's computer.

Antivirus Protection Dates

  • Initial Rapid Release version February 11, 2002
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version February 11, 2002
  • Latest Daily Certified version August 09, 2016 revision 001
  • Initial Weekly Certified release date February 13, 2002

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.


Technical Description


When Backdoor.EggHead is executed, it does the following:

It creates the folder %systemroot%\System32\Vchost and then copies all of its program files into that folder.

NOTE: %systemroot% is a variable. The worm locates the Windows folder (by default this is C:\Windows or C:\Winnt).

Some files are also copied to the %systemroot% folder.

Those files are the following:

  • Services.exe
  • Pskill.exe
  • B.bat
  • Tcpsvcs.exe
  • Good_client.exe.

NOTE: Some of the files that are used by this Trojan are not malicious. The files are part of legitimate programs that are being exploited by Backdoor.EggHead. These files are not detected as Backdoor.EggHead.

Backdoor.EggHead loads itself each time the computer starts by adding the following and registry keys and values:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Events
"Type" = dword:00000010
"Start" = dword:00000002
"ErrorControl" = dword:00000001
"ImagePath" = "%systemroot%\services.exe"
"DisplayName" = "Events"
"ObjectName" = "LocalSystem"
"Description" = "Logs event messages issued by system,.  Event Log reports contain information that can be useful in diagnosing problems.  Reports are viewed in Event Viewer."

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Events\Parameters
"FireStarter" = "C:\WINNT\system32\svchost\inetinfo.exe 254.dll"
"WorkingDir" = "C:\WINNT\system32\svchost"
"ProcessMonitorEnabled" = dword:00000001
"ProcessMonitorFrequency" = dword:00001388
"ProcessAutoRestart" = dword:00000001
"ProcessAffinityMask" = dword:00000000
"ProcessPriority" = dword:00000000

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\TlntSvr
"DependOnService" = "RpcSs.TcpI"
"Description" = "Allows a remote user to log on to the system and run console programs using the command line."
"DisplayName" = "Telnet"
"ErrorControl" = dword:00000001
"ImagePath" = "%SystemRoot%\system32\tlntsvr.exe"
"ObjectName" = "LocalSystem"
"Start" = dword:00000003
"Type" = dword:00000010

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\TlntSvr\Enum
"0" = "Root\LEGACY_TLNTSVR\0000"
"Count" = dword:00000001
"NextInstance" = dword:00000001

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\TelnetServer\1.0
"AllowTrustedDomain" = dword:00000001
"DefaultDomain" = "."
"DefaultShell" = %SystemRoot%\system32\cmd.exe /q /k
"LoginScript" = %SystemRoot%\system32\login.cmd
"MaxConnections" = dword:0000003f
"MaxFailedLogins" = dword:00000003
"NTLM" = dword:00000000
"TelnetPort" = dword:00001a8e
"AltKeyMapping" = dword:00000001
"Termcap" = "%SystemRoot%\system32\termcap"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\TelnetServer\1.0\Performance
"NumThreadsPerProcessor" = dword:00000002

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanserver\parameters
"AutoShareServer" = dword:00000000
"AutoShareWks" = dword:00000000

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\RemoteRegistry
"Start" = dword:00000003
"Type" = dword:00000020

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.


Removal


Delete files detected as Backdoor.EggHead, delete the legitimate files that are dropped by the Trojan, and remove references that it added to the registry.

To delete the Trojan itself:

  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
  3. Run a full system scan.
  4. Delete all files that are detected as Backdoor.EggHead.

To delete the legitimate files that it dropped:
Use Windows Explorer to delete the \%systemroot%\System32\Vchost folder. Also, open the %systemroot% folder, and delete any of the following files that are still there after running the scan:
  • Services.exe
  • Pskill.exe
  • B.bat
  • Tcpsvcs.exe
  • Good_client.exe

NOTE: %systemroot% is a variable. On default installations of Windows NT/2000/XP systems, this is C:\Winnt.

To edit the registry:

CAUTIONS:
  • We strongly recommend 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 only the keys that are specified. Read the document How to back up the Windows registry for instructions.
  • The removal of the keys or values can be somewhat complicated. The entire key should be removed if nothing else is in it other than the values that are noted in the write-up, and if it has no other subkeys. However, in some cases, the key may have other values or subkeys that were added when the system was installed or during the installation of other programs. If you are not sure of what to do for a particular key, we suggest that you obtain the services of a qualified computer consultant.
  1. Click Start, and click Run. The Run dialog box appears.
  2. Type regedit and then click OK. The Registry Editor opens.
  3. Browse to and select in turn each of the keys described (in bold) in the Technical Description. Either delete the key itself if it contains no values or subkeys other than as shown, or delete the values that were added.
  4. Exit the registry editor when finished.


Writeup By: Atli Gudmundsson