Analysis by: RonJay Kristoffer Caragay
ALIASES:

DoS:Linux/Xorddos.A (Microsoft); Linux/DDoS-BH (Sophos); Trojan.Linux.Xorddos (Ikarus); Linux/DDoS-Xor.A (McAfee); a variant of Linux/Xorddos.C trojan (ESET-NOD32); Unix/XorDDOS.A (exact) (F-Prot); Linux.Xorddos (Symantec)

 PLATFORM:

UNIX, LINUX

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware, Downloaded from the Internet

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It does not have any propagation routine.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It also has rootkit capabilities, which enables it to hide its processes and files from the user.

  TECHNICAL DETAILS

File Size: 625,718 bytes
File Type: ELF
Memory Resident: Yes
Initial Samples Received Date: 26 Nov 2015
Payload: Steals information, Connects to URLs/IPs

Arrival Details

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This backdoor drops the following copies of itself into the affected system:

  • /lib/libudev.so

Autostart Technique

This backdoor drops the following files:

  • /etc/cron.hourly/gcc.sh (Cron is a time-based job scheduler in Unix-like computer operating systems)

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Execute files
  • Download files
  • Update Malware
  • Delete Files
  • Terminate Process
  • Remove Services
  • Remove Self
  • Perform DDoS attack

It connects to the following websites to send and receive information:

  • aaa.{BLOCKED}456.com:6001
  • aaa.{BLOCKED}t456.com:6001

Rootkit Capabilities

This backdoor also has rootkit capabilities, which enables it to hide its processes and files from the user.

Download Routine

This backdoor connects to the following URL(s) to download its configuration file:

  • www1.{BLOCKED}t456.com/dd.rar

Information Theft

This backdoor gathers the following data:

  • Memory Information
  • CPU Information
  • Network Speed
  • PID of Running Process
  • MD5 of Running Process

Other Details

This backdoor does the following:

  • Copy the file /lib/libudev.so as:
    • /usr/bin/{random 10 characters}
    • /bin/{random 10 characters}
    • /tmp/{random 10 characters}
  • Drops a shell script in /etc/init.d folder which setups the auto-start mechanism of the malware.
  • Creates symbolic links which points to the script in /etc/init.d:
    • /etc/rc{1-5}.d/S90{random numbers}
    • /etc/rc.d/rc{1-5}.d/S90{random numbers}
  • Get the magic string value from the file /var/run/gcc.pid
  • Read the following from its configuration file:
    • md5 - checksum of file
    • denyip - open communication with an IP
    • filename - list of filename
    • rmfile - files to remove

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.174.03
FIRST VSAPI PATTERN DATE: 26 Nov 2015
VSAPI OPR PATTERN File: 12.175.00
VSAPI OPR PATTERN Date: 27 Nov 2015

Scan your computer with your Trend Micro product to delete files detected as ELF_XORDDOS.AR. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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