Download.Trojan connects to the Internet and downloads other Trojan horses or components.

Variants:  Trojan Horse
Type:  Trojan Horse
Infection Length:  varies
Systems Affected:  Windows 95, Windows 98, Windows NT, Windows 2000, Windows XP, Windows Me


Virus Definitions (Intelligent Updater) *

June 11, 2001

Virus Definitions (LiveUpdate™) **

June 13, 2001


*

Intelligent Updater definitions are released daily, but require manual download and installation.
Click here to download manually.

**

LiveUpdate virus definitions are usually released every Wednesday.
Click here for instructions on using LiveUpdate.



Wild
Number of infections: 0 - 49
Number of sites: 0 - 2
Geographical distribution: Low
Threat containment: Easy
Removal: Easy

Threat Metrics
       

Wild:
Low

Damage:
Low

Distribution:
Low



Download.Trojan does the following:
Goes to a specific Web or FTP site that its author created and attempts to download new Trojans, viruses, worms, or their components.
After the Trojan downloads the files, it executes them.






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.

Disable System Restore (Windows Me/XP).
Update the virus definitions.
Restart the computer in Safe mode (Windows 95/98/Me/2000/XP) or VGA mode (Windows NT).
Run a full system scan and delete all the files detected as Download.Trojan.
Clear Internet Explorer History and files, if needed.

For specific details on each of these steps, read the following instructions.

1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

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"

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder," Article ID: Q263455.

2. 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).

The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. Restarting the computer in Safe mode or VGA mode
For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, refer to the document, "How to start the computer in Safe Mode."
For Windows NT 4 users, restart the computer in VGA mode.


4. Scanning for and deleting the infected files
Start your Symantec antivirus program and make sure that it is configured to scan all the files.
For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan all files."
Run a full system scan.
If any files are detected as infected with Download.Trojan, click Delete. If your Symantec antivirus program detects any infected files that it cannot delete, record the location of the file and the file name. Then do one of the following:
If the file is in a location other than the Temporary Internet Files folder, restart the computer in Safe mode a second time. Then use Windows Explorer, browse to and delete that particular file. Once this is done, restart the computer in Normal mode. For instructions, read the section on returning to Normal mode in the document, "How to start the computer in Safe Mode."
If the file is in the Temporary Internet Files folder, write down the entire path and file name. Then go on to section 5.

5. Clearing the Temporary Internet Files folder
Restart the computer in Normal mode. For instructions, read the section on returning to Normal mode in the document "How to start the computer in Safe Mode."

Log onto the computer using the name that was shown in the path that you wrote down in step 4c.

For example, if the path was:

C:\Documents and Settings\Linda\Local Settings\Temporary Internet Files\qrwmqczd.dll

log on to the computer as Linda.


Start Internet Explorer.
Click the Tools menu > Internet Options.
In the Temporary Internet Files section, click the Delete Files button.
Check "Delete all offline content," and then click OK.