Linux.Hijacker.Worm

SUMMARY

This is a worm that attempts to insert itself onto systems running Red Hat Linux 6.2 and 7.x, and possibly other System V-based Linux versions, that have already been compromised by any other backdoor that has root privileges. It then attempts to remove any other backdoor Trojans on that system, and then tries to spread itself to other similar system across the Internet.

NOTE: If this worm is discovered on a system, it indicates the system was previously compromised

Protection

• Virus Definitions (Intelligent Updater) May 18, 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

Distribution

• Distribution Level: Medium

TECHNICAL DETAILS

This worm searches the Internet for System V-based Linux systems that have been compromised by a backdoor Trojan that may have gained root access. It then remotely launches a module that starts a shell script named w0rmstart.sh. This script attempts to download a compressed file that contains several different components. These components build a stealth tool that helps to hide the worm, configures anonymous FTP on the system, removes any other backdoor Trojans that it finds in /etc/inetd.conf, and then begins searching other IP addresses for other similar Linux system on the Internet.

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

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 Linux.Hijacker.Worm, choose Delete.