The Conficker Worm

Tomorrow -- April 1 -- is D-Day for Conficker, as whatever nasty payload it's packing is currently set to activate. What happens come midnight is a mystery: Will it turn the millions of infected computers into spam-sending zombie robots? Or will it start capturing everything you type -- passwords, credit card numbers, etc. -- and send that information back to its masters?

Or not. As Slate notes, Conficker is scheduled to go "live" on April 1, but whoever's controlling it could choose not to wreak havoc but instead do absolutely nothing, waiting for a time when there's less heat. They can do this because the way Conficker is designed is extremely clever: Rather than containing a list of specific, static instructions, Conficker reaches out to the web to receive updated marching orders via a huge list of websites it creates. Conficker.C -- the latest bad boy -- will start checking 50,000 different semi-randomly-generated sites a day looking for instructions, so there's no way to shut down all of them. If just one of those sites goes live with legitimate instructions, Conficker keeps on trucking.

Conficker's a nasty little worm that takes serious efforts to bypass your security defenses, but you aren't without some tools in your arsenal to protect yourself.

Your first step should be the tools you already have: Windows Update, to make sure your computer is fully patched, and your current antivirus software, to make sure anything that slips through the cracks is caught.

But if Conficker's already on your machine, it may bypass certain subsystems and updating Windows and your antivirus at this point may not work. If you are worried about anything being amiss -- try booting into Safe Mode, which Conficker prevents, to check -- you should run a specialized tool to get rid of Conficker.

Microsoft offers a web-based scanner (note that some users have reported it crashed their machines; I had no trouble with it), so you might try one of these downloadable options instead: Symantec's Conficker (aka Downadup) tool, Trend Micro's Cleanup Engine, or Malwarebytes. Conficker may prevent your machine from accessing any of these websites, so you may have to download these tools from a known non-infected computer if you need them. Follow the instructions given on each site to run them successfully. (Also note: None of these tools should harm your computer if you don't have Conficker.)

As a final safety note, all users -- whether they're worried about an infection or know for sure they're clean -- are also wise to make a full data backup today.

What won't work? Turning your PC off tonight and back on on April 2 will not protect you from the worm (sorry to the dozens of people who wrote me asking if this would do the trick). Temporarily disconnecting your computer from the web won't help if the malware is already on your machine -- it will simply activate once you connect again. Changing the date on your PC will likely have no helpful effect, either. And yes, Macs are immune this time out. Follow the above instructions to detect and remove the worm.

W32.Downadup Removal Tool

Discovered: January 13, 2009

Type: Removal Information

This tool is designed to remove the infections of:

Important:

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 reinfect 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.

For further information on the vulnerability and patches to resolve it please refer to the following document:
Microsoft Windows Server Service RPC Handling Remote Code Execution Vulnerability
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 FixDwndp.exe file from: http://www.symantec.com/content/en/us/global/removal_tool/threat_writeups/FixDwndp.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 FixDwndp.exe file to start the removal tool.
Click Start to begin the process, and then allow the tool to run.

NOTE: If you have any problems when you run the tool, or it does nor appear to remove the threat, restart the computer in Safe mode and run the tool again.
Restart the computer.
Run the removal tool again to ensure that the system is clean.
If you are running Windows Me/XP, then reenable 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 the threat 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 Removal Tool does the following:

Terminates the associated processes
Deletes the associated files
Deletes the registry values added by the threat
Removes the scheduled jobs created by the threat

Switches
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, FixDwndp.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.)
/NOCANCEL
Disables the cancel feature of the removal tool.
/NOFILESCAN
Prevents the scanning of the file system.
/NOVULNCHECK
Disables checking for unpatched files.
/FORCEJOBSREPAIR
Removes the created scheduled jobs.

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\FixDwndp.exe" /EXCLUDE=M:\ /LOG=c:\FixDwndp.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\FixDwndp.exe" /NOFILESCAN /LOG=c:\FixDwndp.txt

Note: You can give the log file any name and save it to any location.

Digital signature
For security purposes, the removal tool is digitally signed. Symantec recommends that you use only copies of the removal tool 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 the removal tool.

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:

Windows 95/98/Me:
command

Windows NT/2000/XP:
cmd
Click OK.
In the command window, type the following, pressing Enter after typing each line:

cd\
cd downloads
chktrust -i FixDwndp.exe
You should see one of the following messages, depending on your operating system:

Windows XP SP2:
The Trust Validation Utility window will appear.

Under Publisher, click the Symantec Corporation link. The Digital Signature Details appears.
Verify the contents of the following fields to ensure that the tool is authentic:

Name: Symantec Corporation
Signing Time: 03/30/2009 10:53:57 AM

All other operating systems:
You should see the following message:

Do you want to install and run "FixDwndp.exe" signed on March 30, 2009 10:53:57 AM and distributed by Symantec Corporation?

Notes:
The date and time in the digital signature above are based on Pacific time. They will be adjusted your computer's time zone and Regional Options settings.

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 or Run to close the dialog box.
Type exit, and then press Enter. (This will close the MS-DOS session.)

BEWARE

Last-minute Conficker survival guide

W32.Downadup Removal Tool