Backdoor.Linux.XORDDOS.AE

 Analysis by: Patrick Noel Collado

 ALIASES:

HEUR:Trojan-DDoS.Linux.Agent.g (Kaspersky), ELF:Xorddos-AD [Trj] (Avast)

 PLATFORM:

Linux

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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:

253,312 bytes

File Type:

ELF

Memory Resident:

Yes

Initial Samples Received Date:

04 Jun 2020

Payload:

Drops files, 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
  • /usr/bin/{random}

Autostart Technique

This Backdoor drops the following files:

  • /etc/cron.hourly/gcc4.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
  • Hide Files
  • Create Services
  • Create Directory
  • Hide Port
  • Copy Files

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

  • {BLOCKED}.{BLOCKED}.9.228:53

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/{random characters} folder which setups the auto-start mechanism of the malware.
  • Creates symbolic links which points to the script in /etc/init.d/{random characters}:
    • /etc/rc{1-5}.d/S90{random numbers}
    • /etc/rc.d/rc{1-5}.d/S90{random numbers}
  • 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
  • Uses the following User Agents:
    • POST/GET %s HTTP/1.1 /
      Accept: */*
      Accept-Language: zh-cn
      User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; SV1; TencentTraveler ;.NET CLR 1.1.4322)
      Connection: Keep-Alive
      Host:
      Content-Type: application/x-www-form-urlencoded
  • Get the magic string value from the file /var/run/gcc.pid
  • It modify /bin/chkconfig to add its copy as a service.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.910.04

FIRST VSAPI PATTERN DATE:

04 Jun 2020

VSAPI OPR PATTERN File:

15.911.00

VSAPI OPR PATTERN Date:

05 Jun 2020

Scan your computer with your Trend Micro product to delete files detected as Backdoor.Linux.XORDDOS.AE. 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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