Backdoor.Graybird is a back door Trojan Horse that gives its creator unauthorized access to your computer. The existence of the file, Svch0st.exe, is an indication of a possible infection. Backdoor.Graybird is a Delphi application.
When Backdoor.Graybird runs, it performs the following actions:
Copies itself as one of the following filenames:
%System%\Svch0st.exe
%System%\Winlogon.exe
%System%\Explorer.exe
%System%\ravmond.exe
NOTE: %System% is a variable. The Trojan locates the System folder and copies itself to that location. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).
Creates one of the following values, or a similar value, depending on the variant:
If the operating system is Windows 95/98/Me, the Trojan adds the line to the [windows] section of the Win.ini file:
run = C:\WINDOWS\SYSTEM\SVCH0ST.EXE
so that the Trojan runs when you start Windows.
Attempts to access the password cache stored on your computer. The cached passwords include, amongst others, the modem and dialup passwords, URL passwords, and share passwords.
Intercepts keystrokes allowing Backdoor.Graybird to steal confidential information.
Once Backdoor.Graybird is installed, it waits for the commands from the remote client.
These commands allow the Trojan's creator to perform any of the following actions:
Deliver system and network information to the Trojan's creator, including the login names and cached network passwords.
Install an FTP server, allowing the hacker to use the compromised computer as a temporary storage device.
Open or close the CD-ROM drive and perform other annoying actions.
Download and execute files.
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.
The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
Update the virus definitions.
Do one of the following:
Windows 95/98/Me: Restart the computer in Safe mode.
Windows NT/2000/XP: End the Trojan process.
Run a full system scan and delete all the files detected as Backdoor.Graybird.
Reverse the changes that the Trojan made to the registry.
Reverse the changes that the Trojan made to the Win.ini file (Windows 95/98/Me only).
For details on each of these steps, 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 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).
2. Restarting the computer in Safe mode or ending the Trojan process
Windows 95/98/Me Restart the computer in Safe mode. All the Windows 32-bit operating systems, except for Windows NT, can be restarted in Safe mode. For instructions on how to do this, read the document, "How to start the computer in Safe Mode."
Windows NT/2000/XP
To end the Trojan process:
Press Ctrl+Alt+Delete once.
Click Task Manager.
Click the Processes tab.
Double-click the Image Name column header to alphabetically sort the processes.
Scroll through the list and look for Svch0st.exe.
If you find the file, click it, and then click End Process.
Exit the Task Manager.
3. Scanning for and deleting the infected files
Start your Symantec antivirus program and make sure that it is configured to scan all the files.
If any files are detected as infected with Backdoor.Graybird, click Delete.
4. Reversing the changes made to 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.
Click Start, and then click Run. (The Run dialog box appears.)
4. Reversing the changes made to the Win.ini file
If you are running Windows 95/98/Me, follow these steps:
The function you perform depends on your operating system:
Windows 95/98: Go to step b.
Windows Me: If you are running Windows Me, the Windows Me file-protection process may have made a backup copy of the Win.ini file that you need to edit. If this backup copy exists, it will be in the C:\Windows\Recent folder. Symantec recommends deleting this file before continuing with the steps in this section. To do this:
Start Windows Explorer.
Browse to and select the C:\Windows\Recent folder.
In the right pane, select the Win.ini file and delete it. The Win.ini file will be regenerated when you save your changes to it in step f.
Click Start, and then click Run.
Type the following:
edit c:\windows\win.ini
and then click OK. (The MS-DOS Editor opens.)
NOTE: If Windows is installed in a different location, make the appropriate path substitution.
In the [windows] section of the file, look for a line similar to:
run = C:\WINDOWS\SYSTEM\SVCH0ST.EXE
If this line exists, delete the entire line.
Click File, and then click Save.
Click File, and then click Exit.
Revision History:
May 29, 2003: Update technical description with additional content pertaining to minor variants.
