Backdoor.Linux.RSHell.A

June 14, 2019
 Analysis by: Noel Anthony Llimos
 ALIASES:

HEUR:Trojan.Linux.Agent.du (Kaspersky)

 PLATFORM:

Linux

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

  • Threat Type: Trojan

  • Destructiveness: Yes

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet

This Trojan 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. It connects to a website to send and receive information.

  TECHNICAL DETAILS

Payload:

Connects to URLs/IPs

Arrival Details

This Trojan 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 Trojan drops a copy of itself in the following folders using different file names:

  • /bin/netstat ← the original netstat is moved with a different filename which is "/bin/scnetstat"

Other System Modifications

This Trojan deletes the following files:

  • /bin/ddus-uidgen
  • /etc/init.d/acpidtd
  • /etc/rc.d/rc*.d/S01acpidtd
  • /etc/ld.sc.conf

Backdoor Routine

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

  • Execute shell commands

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

  • {BLOCKED}.{BLOCKED}.30.212
  • {BLOCKED}.{BLOCKED}.33.59
  • {BLOCKED}.{BLOCKED}.32.135
  • {BLOCKED}.{BLOCKED}.202.186
  • {BLOCKED}.{BLOCKED}.116.233
  • {BLOCKED}.{BLOCKED}.214.158
  • {BLOCKED}.{BLOCKED}.90.199
  • {BLOCKED}.{BLOCKED}.199.236
  • {BLOCKED}.{BLOCKED}.33.242

Other Details

This Trojan does the following:

  • Names the executed process with any within the following list:
    • [aio]
    • [async]
    • [ata]
    • [ata_aux]
    • [bdi-default]
    • [cpuset]
    • [crypto]
    • [ecryptfs-kthrea]
    • [eventsli>[ext4-dio-unwrit]
    • [flush-251:0]
    • [flush-8:0]
    • [jbd2]
    • [kacpi_hotplug]
    • [kacpi_notify]
    • [kacpid]
    • [kblockd]
    • [kconservative]
    • [kdmflush]
    • [khelper]
    • [khubd]
    • [khungtaskd]
    • [kintegrityd]
    • [kmmcd]
    • [kmpath_handlerd]
    • [kmpathd]
    • [kondemand]
    • [kpsmoused]
    • [kseriod]
    • [ksmd]
    • [ksnapd]
    • [ksoftirqd]
    • [kstriped]
    • [ksuspend_usbd]
    • [kswapd0]
    • [kswapd1]
    • [kthreadd]
    • [migration]
    • [netns]
    • [pm]
    • [scsi_eh_0]
    • [sync_supers]
    • [usbhid_resumer]
    • [watchdog]
    • [xfs_mru_cache]
    • [xfsaild]
    • [xfsbufd]
    • [xfsconvertd]
    • [xfsdatad]
    • [xfslogd]
    • [xfssyncd]

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.172.06

FIRST VSAPI PATTERN DATE:

13 Jun 2019

VSAPI OPR PATTERN File:

15.173.00

VSAPI OPR PATTERN Date:

14 Jun 2019

Scan your computer with your Trend Micro product to delete files detected as Backdoor.Linux.RSHell.A. 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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