Linux.Ramen.Worm

SUMMARY

Linux.Ramen is a Linux worm that attacks machines running the Linux Red Hat 6.2 or 7.0 operating system. This worm does not execute on systems running Microsoft Windows. The worm attempts to use unpatched versions of rpc.statd, wuftpd, and LPRng.

Protection

• Virus Definitions (Intelligent Updater) January 17, 2001

Threat Assessment

Wild

• Wild Level: Medium
• Number of Infections: 50 - 999
• Number of Sites: More than 10
• Geographical Distribution: Medium
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Medium
• Modifies Files: Modifies index.html, defacing website

Distribution

• Distribution Level: Medium
• Ports: 27374
• Target of Infection: Redhat Linux 6.2, 7.0

TECHNICAL DETAILS

Linux.Ramen is a worm that is in the wild. It spreads over the Internet onto machines running Red Hat 6.2 or Red Hat 7.0. Since this worm only operates on the Linux operating system, users of Microsoft Windows will be largely unaffected.

The worm starts by running a shell script called start.sh. This script calls a random number generator that returns a random class B subnet IP address. The worm will attempt to copy itself to these IP addresses. The worm then starts an HTTP server on port 27374 to serve out itself to newly infected machines and also patches the exploits that it used to gain access to the system.

By plugging these holes, the worm will not reinfect the machine. In addition, as an indirect effect, other hackers will not be able to gain access to these machines using these exploits.

The worm uses a tool called synscan which has been modified to fit its needs. Using this tool, the worm contacts a randomly generated IP address and checks the FTP banner to determine if the machine is running Red Hat Linux 6.2 or Red Hat Linux 7.0. For machines running Red Hat 6.2, the worm will attempt to exploit a vulnerable rpc.statd or wuftpd service. For Red Hat 7.0, the worm tries to exploit an LPRng bug to gain access to the system.

Once the worm gains access to the system using the above exploits, the worm copies itself as a tar.gz package onto the newly compromised system. The worm does so by downloading the tar.gz package from the infecting machine by means of the worm-created HTTP service running on port 27374.

The worm extracts the contents of this package into the tmp directory on the attacked machine and executes start.sh, activating the worm on the newly infected machine.

An email message is also sent to an anonymous Yahoo! and Hotmail email account specifying the IP address of the attacked machine. Most likely, these email accounts belong to the author of this worm allowing the author to keep track of machines that are infected.

Finally, the worm replaces Index.html to show the following contents:

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 Linux.Ramen.Worm:

1. Delete the files detected by Norton AntiVirus.
2. Install the patches that will fix these mentioned vulnerabilities. These patches are already available for download at the Red Hat website at the following locations:
   • RedHat 7.0 Security Advisories - http://www.redhat.com/support/errata/rh7-errata-security.html
   • RedHat 6.2 Security Advisories - http://www.redhat.com/support/errata/rh62-errata-security.html