Discovered: March 18, 2005
Updated: December 05, 2005 12:00:00 AM
Type: Removal Information
Symantec Security Response has developed a removal tool to clean the infections of the following variants of the W32.Serflog worm:
If you are on a network or have a full-time connection to the Internet, such as a DSL or cable modem, disconnect the computer from the network and Internet. Disable or password-protect file sharing, or set the shared files to Read Only, before reconnecting the computers to the network or to the Internet. Because this worm spreads by using shared folders on networked computers, to ensure that the worm does not re-infect the computer after it has been removed, Symantec suggests sharing with Read Only access or by using password protection.
For instructions on how to do this, refer to your Windows documentation, or the document, "How to configure shared Windows folders for maximum network protection."
If you are removing an infection from a network, first make sure that all the shares are disabled or set to Read Only.
This tool is not designed to run on Novell NetWare servers. To remove this threat from a NetWare server, first make sure that you have the current virus definitions, and then run a full system scan with the Symantec antivirus product.
How to download and run the tool
Important: You must have administrative rights to run this tool on Windows NT 4.0, Windows 2000, or Windows XP.
Note for network administrators: If you are running MS Exchange 2000 Server, we recommend that you exclude the M drive from the scan by running the tool from a command line, with the Exclude switch. For more information, read the Microsoft knowledge base article, "XADM: Do Not Back Up or Scan Exchange 2000 Drive M" (Article 298924).
Follow these steps to download and run the tool:
Download the FixSflog.exe file from: http://securityresponse.symantec.com/avcenter/FixSflog.exe
Save the file to a convenient location, such as your Windows desktop.
Optional: To check the authenticity of the digital signature, refer to the "Digital signature" section later in this writeup.
Note: If you are sure that you are downloading this tool from the Security Response Web site, you can skip this step. If you are not sure, or are a network administrator and need to authenticate the files before deployment, follow the steps in the "Digital signature" section before proceeding with step 4.
Close all the running programs.
If you are on a network or if you have a full-time connection to the Internet, disconnect the computer from the network and the Internet.
If you are running Windows Me or XP, turn off System Restore. 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"
Locate the file that you just downloaded.
Double-click the FixSflog.exe file to start the removal tool.
Click Start to begin the process, and then allow the tool to run.
Restart the computer.
Run the removal tool again to ensure that the system is clean.
If you are running Windows Me/XP, then re-enable System Restore.
If you are on a network or if you have a full-time connection to the Internet, reconnect the computer to the network or to the Internet connection.
Run LiveUpdate to make sure that you are using the most current virus definitions.
When the tool has finished running, you will see a message indicating whether W32.Serflog has infected the computer. The tool displays results similar to the following:
Total number of the scanned files
Number of deleted files
Number of repaired files
Number of terminated viral processes
Number of fixed registry entries
What the tool does
The W32.Serflog Removal Tool does the following:
Terminates the W32.Serflog processes
Deletes the W32.Serflog files
Deletes the registry values that W32.Serflog has added
Deletes the values added to the Hosts file
The following switches are designed for use by network administrators:
/HELP, /H, /? Displays the help message.
/NOFIXREG Disables the registry repair (We do not recommend using this switch).
/SILENT, /S Enables the silent mode.
/LOG=[PATH NAME] Creates a log file where [PATH NAME] is the location in which to store the tool's output. By default, this switch creates the log file, FixSflog.log, in the same folder from which the removal tool was executed.
/MAPPED Scans the mapped network drives. (We do not recommend using this switch. See the following Note.)
/START Forces the tool to immediately start scanning.
/EXCLUDE=[PATH] Excludes the specified [PATH] from scanning. (We do not recommend using this switch. See the following Note.)
/NOFILESCAN Prevents the scanning of the file system.
Important: Using the /MAPPED switch does not ensure the complete removal of the virus on the remote computer, because:
The scanning of mapped drives scans only the mapped folders. This may not include all the folders on the remote computer, which can lead to missed detections.
If a viral file is detected on the mapped drive, the removal will fail if a program on the remote computer uses this file.
Therefore, you should run the tool on every computer.
The /EXCLUDE switch will only work with one path, not multiple. An alternative is the /NOFILESCAN switch followed by a manual scan with AntiVirus. This will let the tool alter the registry. Then, scan the computer with AntiVirus with current virus definitions. With these steps, you should be able to clean the file system.
The following is an example command line that can be used to exclude a single drive:
"C:\Documents and Settings\user1\Desktop\FixSflog.exe" /EXCLUDE=M:\ /LOG=c:\Serflog.txt
Alternatively, the command line below will skip scanning the file system, but will repair the registry modifications. Then, run a regular scan of the system with proper exclusions:
"C:\Documents and Settings\user1\Desktop\FixSflog.exe" /NOFILESCAN /LOG=c:\Serflog.txt
Note: You can give the log file any name and save it to any location.
For security purposes, FixSflog.exe is digitally signed. Symantec recommends that you use only copies of FixSflog.exe that have been directly downloaded from the Symantec Security Response Web site.
If you are not sure, or are a network administrator and need to authenticate files before deployment, you should check the authenticity of the digital signature.
Follow these steps:
Go to http://www.wmsoftware.com/free.htm.
Download and save the Chktrust.exe file to the same folder in which you saved FixSflog.exe .
Note: Most of the following steps are done at a command prompt. If you downloaded the removal tool to the Windows desktop, it will be easier if you first move the tool to the root of the C drive. Then save the Chktrust.exe file to the root of C as well.
(Step 3 to assume that both the removal tool and Chktrust.exe are in the root of the C drive.)
Click Start > Run.
Type one of the following:
In the command window, type the following, pressing Enter after typing each line:
chktrust -i FixSflog.exe
You should see the message:
Do you want to install and run "W32.Serflog Removal Tool" signed on 03/18/2005 08:05 AM and distributed by Symantec Corporation?
The date and time displayed in this dialog box will be adjusted to your time zone, if your computer is not set to the Pacific time zone.
If you are using Daylight Saving time, the displayed time will be exactly one hour earlier.
If this dialog box does not appear, there are two possible reasons:
The tool is not from Symantec: Unless you are sure that the tool is legitimate and that you downloaded it from the legitimate Symantec Web site, you should not run it.
The tool is from Symantec and is legitimate: However, your operating system was previously instructed to always trust content from Symantec. For information on this and on how to view the confirmation dialog again, read the document, "How to restore the Publisher Authenticity confirmation dialog box."
Click Yes to close the dialog box.
Type exit, and then press Enter. (This will close the MS-DOS session.)