Trojan.Eurosol

SUMMARY

Trojan.Eurosol installs itself on an infected system so that it is run at startup. It does this by modifying the System.ini file and appending itself to the shell = Explorer.exe line in the [boot] section. It also creates a copy of itself in the Windows folder as the system file NetBios32.exe.

Protection

• Virus Definitions (Intelligent Updater) May 21, 2001

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: Low
• Modifies Files: system.ini

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

This Trojan will also attack installations of the ATGuard firewall if it is present on the infected computer. It will modify the registry so that the NetBios32.exe file can execute and allow outbound connections to the server ftp.hobox.ru. If the WebMoney program is installed, the Trojan attempts to send sensitive information related to WebMoney (http:/ /www.webmoney.ru) to the FTP site.

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 Trojan, attempt to repair files detected as Trojan.Eurosol, restore the shell= line, and delete the keys that it added to the registry.

To scan with Norton AntiVirus:

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and then run a full system scan, making sure that NAV is set to scan all files.
3. If any files are detected as Trojan.Eurosol, choose Repair. If any files cannot be repaired, choose Delete.

To edit the System.ini file:

1. Click Start, and click Run.
2. Type the following and then click OK.
   
   edit c:windowssystem.ini
   
   The MS-DOS Editor opens.
   
   NOTE: If you have installed Windows to a different location, make the appropriate substitution.
   
3. In the [boot] section of the file, look for an entry similar to the following:
   
   shell=Explorer.exe <additional text added by Trojan>
   
4. Delete all text (on the shell=Explorer.exe line only) that is to the right of Explorer.exe. When you are done, the line should read:
   
   shell=Explorer.exe
   
5. Click File, click Exit, and then click Yes when prompted to save the changes.

To edit the registry:
If ATGuard is installed on your system, you will need to reverse the registry modifications made by the Trojan horse.

CAUTION: We strongly recommend that you back up the system registry before making any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure you modify only the keys specified. Please see the document How to back up the Windows registry before proceeding.

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 and delete the following keys:
   
   HKEY_LOCAL_MACHINESoftwareWRQIAMFirewallObjectsApplicationsNETBIO32.EXE
   
   HKEY_LOCAL_MACHINESoftwareWRQIAMFirewallObjectsIPHostsftp.hotbox.ru
   
   HKEY_LOCAL_MACHINESoftwareWRQIAMFirewallObjectsIPFilterRulesRule#
   
   (where Rule# is the Rule key which refers to the information related to ftp.hotbox.ru.)
   
4. Click Registry, and then click Exit to save the changes.