Linux.Sorso

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Discovered: July 02, 2003
Updated: February 13, 2007 12:03:54 PM
Also Known As: Worm.Linux.Sorso.a, Backdoor.Linux.Sorso (AVP)
Type: Worm
Systems Affected: Linux


Linux.Sorso is a worm that replicates using a Samba buffer overflow exploit . The worm targets vulnerable installations of the Samba server version 2.2.8a and earlier, version 2.0.10 and earlier, and Samba-TNG version 0.3.2 and earlier. The worm also contains code for a backdoor and a Distributed Denial of Service (DDoS) attack and only affects Linux running on Intel x86 platforms.


Antivirus Protection Dates

  • Initial Rapid Release version July 03, 2003
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version July 03, 2003
  • Latest Daily Certified version August 09, 2016 revision 001
  • Initial Weekly Certified release date July 09, 2003

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Yuhui Huang

Discovered: July 02, 2003
Updated: February 13, 2007 12:03:54 PM
Also Known As: Worm.Linux.Sorso.a, Backdoor.Linux.Sorso (AVP)
Type: Worm
Systems Affected: Linux


When Linux.Sorso is executed, it performs the following actions:

  1. Tries to establish an anonymous SMB session with a Samba server.

  2. Sends a TRANS2_OPEN2 request with invalid parameters containing exploit code.

    NOTE: The worm uses a Linux shell code exploit, which runs only on Intel x86 platforms.

  3. Sends a shell command sequence to the remote shell, which causes the server to download the files from http://www.jx263.com/.

  4. Extracts the downloaded files to /usr/lib/.lib and starts a script called start.sh. This requires the presence of the shell command /bin/sh, wget, and tar in the PATH to properly execute.

  5. Adds several cron jobs to be executed. These jobs include an exploit program to spread itself, a hijacked version of http daemon, a hijacked ps command, a backdoor, and a DDoS program.

  6. Mails the server's IP address, with the /etc/hosts, /etc/passwd, and /etc/shadow files, to hyukie54@163.com and nihao16897888@21cn.com.

  7. Scans random class C-sized networks for Samba hosts and tries to exploit each one found.

  8. Replaces the existing http daemon with a hijacked version, allowing Web access to any file on the machine.

  9. Hides running processes, which the worm created, using the hijacked ps command.

  10. Replaces /sbin/klogd with a backdoor program. Upon receiving an ICMP packet of a specific size, the backdoor program binds to a fixed TCP port and provides a shell running as root.

  11. Generates a list of possible IPs on a random class C-sized network once a day and adds them to a file. The DDoS program goes through every IP address in the file and sends an ICMP request to that particular IP, using a spoofed source address. As a result, all the ICMP echo response packets go to the spoofed IP address and create an ICMP DDOS attack. The spoofed source IP address is www.rising.com.cn.


Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • 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.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a 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.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. 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.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

Writeup By: Yuhui Huang

Discovered: July 02, 2003
Updated: February 13, 2007 12:03:54 PM
Also Known As: Worm.Linux.Sorso.a, Backdoor.Linux.Sorso (AVP)
Type: Worm
Systems Affected: Linux


Once Linux.Sorso attacks a computer, it is difficult to determine what else the computer has been exposed to. In most cases, changes other than those made by the threat will not have occurred. However, the author of the threat may have been able to use the threat to access the computer to make changes to it. Unless you can be absolutely sure that malicious activity has not been performed on the computer, we recommend completely re-installing the operating system.

Writeup By: Yuhui Huang