ELF_SOTDAS.A

August 29, 2014
 Analysis by: Vincent Martin Hermosura
 ALIASES:

HEUR:Trojan-DDoS.Linux.Sotdas.a (Kaspersky), Trojan.Linux.DDoS (Ikarus), Linux/DDoS.Sotdas.A trojan (Esset)

 PLATFORM:

Linux

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

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.

  TECHNICAL DETAILS

File Type:

ELF

Memory Resident:

Yes

Initial Samples Received Date:

20 Aug 2014

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 the following copies of itself into the affected system:

  • /tmp/.sshhdd{random number}

It drops the following file(s)/component(s):

  • /etc/init.d/.SSHH2

Other Details

This Trojan connects to the following possibly malicious URL:

  • by.{BLOCKED}2088:7668

NOTES:

It checks if it is already running in the affected system. It does this by checking the current running {malware file path and file name}. It terminates itself if found running in "/etc/.SSHH2".

If the the current running {malware file path and file name} is in "/tmp/.sshhdd", it will drop a copy of itself as "/tmp/.sshhdd{random number}".

If there is no running copy of itself, it proceeds into its installation routines:

  • Drops copy of itself in "/etc/.SSHH2"
  • Creates symbolic link "/etc/rc2.d/S77.SSHH2" that points to "/etc/init.d/.SSHH2"
  • Creates symbolic link "/etc/rc3.d/S77.SSHH2" that points to "/etc/init.d/.SSHH2"
  • Creates symbolic link "/etc/rc4.d/S77.SSHH2" that points to "/etc/init.d/.SSHH2"
  • Creates symbolic link "/etc/rc5.d/S77.SSHH2" that points to "/etc/init.d/.SSHH2"
  • Runs the dropped copy of itself

The dropped file "/etc/init.d/.SSHH2" contains a commandline that uses setsid to execute "/etc/.SSHH2" in background.

It then deletes itself after execution.

The following dropped files also mentioned above enables the malware to execute at every system startup:

  • "/etc/rc2.d/S77.SSHH2"
  • "/etc/rc3.d/S77.SSHH2"
  • "/etc/rc4.d/S77.SSHH2"
  • "/etc/rc5.d/S77.SSHH2"
  • "/etc/init.d/.SSHH2"

  SOLUTION

Minimum Scan Engine:

9.700

Scan your computer with your Trend Micro product to delete files detected as ELF_SOTDAS.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 this Knowledge Base page for more information.


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