JS.Gigger.A@mm

SUMMARY

JS.Gigger.A@mm is a worm written in JavaScript. It uses Microsoft Outlook and mIRC to spread. It attempts to delete all files on the computer and to format drive C if the computer is successfully restarted.

Protection

• Virus Definitions (LiveUpdate™ Weekly) January 9, 2002
• Virus Definitions (Intelligent Updater) January 9, 2002

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: High
• Large Scale E-mailing: Sends email to all Microsoft Outlook addresses
• Deletes Files: All files
• Modifies Files: Autoexec.bat to delete all files

Distribution

• Distribution Level: High
• Subject of Email: Outlook Express Update
• Name of Attachment: mmsn_offline.htm

TECHNICAL DETAILS

JS.Gigger.A@mm arrives as an email message that has the following characteristics:

Subject: Outlook Express Update
Message: MSNSofware Co.
Attachement: Mmsn_offline.htm

If the worm is executed, it does the following:

It drops the following files:

• C:Bla.hta
• C:B.htm
• C:WindowsSamplesWshCharts.js
• C:WindowsHelpMmsn_offline.htm

It infects .html files.

It adds the line

ECHO y|format c:

to the Autoexec.bat file, so that if the computer is restarted, drive C is reformatted.

Next., it drops a Script.ini file to spread itself by mIRC. Norton AntiVirus (NAV) detects the infected Script.ini as IRC.Worm.gen.

The worm then creates the following registry keys:

HKEY_CURRENT_USERSoftwareMicrosoftWindows Scripting HostSettingsTimeout
HKEY_CURRENT_USERSoftwareTheGraveadUsersv2.0

and adds the value:

NAV DefAlert   %Windows%SAMPLESWSHChart.vbs.

to the registry key

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun

NOTE: If the value NAV DefAlert already exists, it is modified by the worm. This value is used by some versions of Norton AntiVirus. In either case, removing it as directed in the removal instructions will not affect the ability of Norton AntiVirus to run or detect viruses.

Next, if you are connected to a network, the worm searches network drives and copies itself as WindowsStart MenuProgramsStartUpMsoe.hta

Finally, it attempts to delete all files on the local hard drive.

Recommendations

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.

REMOVAL

To remove this worm, delete all files that are detected as JS.Gigger.A@mm, remove the line that the worm added to the Autoexec.bat file, and remove the keys and value that the worm added to the registry. Detailed instructions follow.

NOTE: If the worm was executed and it deleted all files on your computer, you will have to reinstall Windows and all software, and restore other files from a clean backup.

To remove the worm:

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 JS.Gigger.A@mm.

To edit the Autoexec.bat file:

1. Click Start, and click Run.
2. Type the following line, and then click OK.
   
   edit c:autoexec.bat
   
   The MS-DOS Editor opens.
   
3. Look for the line
   
   ECHO y|format c:
   
   If it exists, select the entire line. Be sure that you do not select any other text, and then press Delete.
4. Click File, and click Save.
5. Click File, and click Exit.

To edit the registry:

CAUTION: 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.

1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. Navigate to the following key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
4. In the right pane, delete the following value:
   
   NAV DefAlert
   
5. Navigate to and delete the following keys:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindows Scripting HostSettingsTimeout
   HKEY_CURRENT_USERSoftwareTheGraveadUsersv2.0
   
6. Click Registry, and then click Exit.