Analysis by: Pearl Charlaine Espejo
 Modified by: John Donnie Celestre
ALIASES:

Linux/DDoS-BH (Sophos); Linux.Xorddos (Symantec); Linux/DDoS-Xor.A (McAfee); HEUR:Trojan-DDoS.Linux.Xarcen.a (Kaspersky)

 PLATFORM:

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 executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size: 625,611 bytes
File Type: ELF
Memory Resident: Yes
Initial Samples Received Date: 21 Nov 2016
Payload: Compromises system security, Steals information

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 files:

  • /usr/bin/{random 10 characters}
  • /bin/{random 10 characters}
  • /tmp/{random 10 characters}

It 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)

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 posts the following information to its command and control (C&C) server:

  • http://www1.{BLOCKED}t456.com/dd.rar:1520

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:

  • 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: 12.850.58
FIRST VSAPI PATTERN DATE: 22 Oct 2016
VSAPI OPR PATTERN File: 12.851.00
VSAPI OPR PATTERN Date: 23 Oct 2016

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Identify and terminate files detected as ELF_XORDDOS.SM

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

Search and delete these files

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.  
  • /usr/bin/{random 10 characters}
  • /bin/{random 10 characters}
  • /tmp/{random 10 characters}
  • /lib/libudev.so
  • /etc/cron.hourly/gcc.sh

Step 5

Scan your computer with your Trend Micro product to delete files detected as ELF_XORDDOS.SM. 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 the following Trend Micro Support pages for more information:


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