W32.SillyFDC

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Discovered: February 27, 2007
Updated: September 22, 2014 2:39:17 PM
Type: Worm
Systems Affected: Windows

W32.SillyFDC is a generic detection for worms that spread by copying themselves to removable drives. Certain variants may also copy themselves to mapped drives, while others may download files or perform other malicious activities.

AutoRun is a feature of Windows that allows a drive to be configured so that a particular executable may be run whenever the drive is accessed or connected to another computer. Worms detected as W32.SillyFDC typically use the AutoRun feature to spread.

The term AutoPlay is used to refer to functionality present in Windows XP and later that includes the AutoRun feature. On insertion of media, AutoPlay may prompt the user to select an action that should be taken. Depending on system configuration, these actions may include AutoRun tasks.

Users should note that AutoRun is disabled by default for non-optical removable drives in recent versions of Windows and on systems with certain updates applied.

Symantec strongly recommends that users take steps to control the use of the AutoRun feature and prevent the execution of programs referenced in autorun.inf files. For more information, please see the following document:

How to prevent a virus from spreading using the 'AutoRun' feature.

If a Symantec antivirus product displays a detection alert for this threat, it means the computer is already protected and the Symantec product will effectively remove this threat from the computer.

Antivirus Protection Dates

  • Initial Rapid Release version January 08, 2004
  • Latest Rapid Release version July 15, 2018 revision 017
  • Initial Daily Certified version January 08, 2004
  • Latest Daily Certified version July 15, 2018 revision 002
  • Initial Weekly Certified release date July 12, 2006

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

Writeup By: Henry Bell

Discovered: February 27, 2007
Updated: September 22, 2014 2:39:17 PM
Type: Worm
Systems Affected: Windows

W32.SillyFDC is a generic detection for worms that spread by copying themselves to removable drives. Certain variants may also copy themselves to mapped drives, while others may download files or perform other malicious activities.


Background information

AutoRun is the name given to a feature of Windows that allows an executable to run automatically when a drive is accessed. The AutoRun feature was introduced to allow software vendors to distribute media that was configured to run certain programs on insertion of the USB key, CD or DVD. This was useful as it allowed end users to be shielded from the file system details of program installers and the 'multimedia' packages that were popular at the time.

Malicious individuals were quick to take advantage of this infection vector, though, and many worms are now able to copy themselves and an accompanying autorun.inf file to removable drives. This means that the worms are able to spread when the drives are accessed by an unsuspecting user.


How AutoRun works
In order for a program to execute using AutoRun, a configuration file called autorun.inf must be present in the root folder of the drive. This is a simply a text file that contains information that specifies how the file should be displayed, along with options for its execution.

An autorun.inf file may, for example, be created so that the file %DriveLetter%\setup.exe is executed when the disk is inserted into a computer with AutoRun enabled. Options that specify the icon to be used as well as the label for the disk may also be included.


Worms detected as W32.SillyFDC may also propagate in the same way through other drives, due to the fact that the AutoRun feature works in an equivalent manner on removable, fixed and mapped drives. This includes those that are accessed over a network.

Users should note that the AutoRun feature is disabled by default for non-optical removable drives in recent versions of Windows and on systems with certain updates applied. For more information, please see the following resource:

How to prevent a virus from spreading using the 'AutoRun' feature.


How do these threats arrive on a computer?
Worms detected as W32.SillyFDC typically arrive when an infected removable drive is inserted into the computer, or an infected mapped drive is accessed. Infected files may also be downloaded from file-sharing networks.


Typical behavior
When executed, W32.SillyFDC variants typically copy themselves to the system disk of the compromised computer. They then create files or modify the registry so that they run every time Windows starts. Next, the worms copy themselves to removable and sometimes mapped drives, and at the same time create autorun.inf files so that the copied executables run when the drives are accessed.


Extended behavior
Worms that are detected as W32.SillyFDC may also perform actions that include, but need not be limited to, the following:

  • Download files from a preconfigured URL
  • Copy themselves to network shares
  • Lower security settings
  • Alter Safe Mode settings
  • Modify the hosts file
  • Disable Windows Update and System Restore
  • Bypass the Windows firewall
  • Alter Explorer settings
  • Disable the Task Manager, Registry Editor and other system software

Are there any tell-tale signs?
Although these worms are usually designed to run stealthily, users may notice unusual behavior when W32.SillyFDC worms execute. Unusual or unexpected activity when removable drives are inserted may be an indicator of infection.


What can I do to minimize the risks?
Users should disable the AutoRun feature or be sure to upgrade to a recent version of Windows that has AutoRun disabled by default for non-optical removable media.

As a general rule, users should always run up-to-date antivirus software with real-time protection such as Norton Antivirus, Norton Internet Security, Norton 360 or Symantec Endpoint Protection . In addition, a firewall -- or better still, an Intrusion Prevention System (IPS) -- will help to block download activities initiated by these types of malicious programs. Program controls such as those found in Symantec Endpoint Protection can also help to prevent programs such as these from executing in the first place.


How can I find out more?

Advanced users can submit a sample to Threat Expert to obtain a detailed report of the system and file system changes caused by a threat.

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.

Writeup By: Henry Bell

Discovered: February 27, 2007
Updated: September 22, 2014 2:39:17 PM
Type: Worm
Systems Affected: Windows

You may have arrived at this page either because you have been alerted by your Symantec product about this risk, or you are concerned that your computer has been affected by this risk.

Before proceeding further we recommend that you run a full system scan . If that does not resolve the problem you can try one of the options available below.



FOR NORTON USERS
If you are a Norton product user, we recommend you try the following resources to remove this risk.

Removal Tool


If you have an infected Windows system file, you may need to replace them using from the Windows installation CD .


How to reduce the risk of infection
The following resources provide further information and best practices to help reduce the risk of infection.


FOR BUSINESS USERS
If you are a Symantec business product user, we recommend you try the following resources to remove this risk.

Identifying and submitting suspect files
Submitting suspicious files to Symantec allows us to ensure that our protection capabilities keep up with the ever-changing threat landscape. Submitted files are analyzed by Symantec Security Response and, where necessary, updated definitions are immediately distributed through LiveUpdate™ to all Symantec end points. This ensures that other computers nearby are protected from attack. The following resources may help in identifying suspicious files for submission to Symantec.


Removal Tool

If you have an infected Windows system file, you may need to replace them using from the Windows installation CD .


How to reduce the risk of infection
The following resource provides further information and best practices to help reduce the risk of infection.
Protecting your business network



MANUAL REMOVAL
The following instructions pertain to all current Symantec antivirus products.

1. Performing a full system scan
How to run a full system scan using your Symantec product


2. Restoring settings in the registry
Many risks make modifications to the registry, which could impact the functionality or performance of the compromised computer. While many of these modifications can be restored through various Windows components, it may be necessary to edit the registry. See in the Technical Details of this writeup for information about which registry keys were created or modified. Delete registry subkeys and entries created by the risk and return all modified registry entries to their previous values.

Writeup By: Henry Bell