Analysis by: Karen Ivy Titiwa
ALIASES:

Backdoor.Linux.Dofloo.c (KASPERSKY); ELF/Dofloo.C!tr(FORTINET)

 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: 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: 1,001,465 bytes
File Type: ELF
Memory Resident: Yes
Initial Samples Received Date: 04 Jun 2020
Payload: Launches DoS/DDoS attacks, 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 adds the following processes:

  • sed -i -e '/exit/d' /etc/rc.local
  • sed -i -e '/^\r\n|\r|\n$/d' /etc/rc.local
  • sed -i -e '/%s/d' /etc/rc.local
  • sed -i -e '2 i%s/%s' /etc/rc.local
  • sed -i -e '2 i%s/%s start' /etc/rc.d/rc.local
  • sed -i -e '2 i%s/%s start' /etc/init.d/boot.local

Backdoor Routine

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

  • Initiate DDoS attacks:
    • TCP flood
    • Challenge Collapsar (CC) attack
  • Stop DDoS attack
  • Execute shell commands

Information Theft

This Backdoor gathers the following data:

  • CPU information
  • Memory statistics
  • IP address of infected machine
  • Reads the following information from /proc:
    • /proc/stat
    • /proc/meminfo
    • /proc/cpuinfo
    • /proc/net/dev
    • /proc/self/exe
    • /proc/self/maps
    • /proc/sys/vm/overcommit_memory
    • /proc/sys/kernel/rtsig-max
    • /proc/sys/kernel/ngroups_max
    • /proc/sys/kernel/osrelease
    • /proc/self/fd/%d/%s
    • /proc/self/fd
    • /proc/net

Other Details

This Backdoor opens the following files:

  • /etc/host.conf
  • /etc/resolv.conf
  • /etc/nsswitch.conf
  • /etc/suid-debug
  • /etc/ld.so.cache

  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.DOFLOO.AB 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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