Analysis by: Andrei Castillo
 Modified by: Anthony Joe Melgarejo
ALIASES:

Linux.Fokirtor (Symantec), Linux/Fokirtor.A!tr (Fortinet), Backdoor.Linux.Fokirtor (Ikarus), Linux/Fokirtor.A trojan (ESET)

 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: 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 runs certain commands that it receives remotely from a malicious user. Doing this puts the affected computer and information found on the computer at greater risk.

  TECHNICAL DETAILS

File Size: 58,176 bytes
File Type: ELF
Memory Resident: Yes
Initial Samples Received Date: 16 Nov 2013
Payload: 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.

Backdoor Routine

This backdoor executes the following command(s) from a remote malicious user:

  • Execute arbitrary commands
  • Steal files

Information Theft

This backdoor gathers the following data:

  • Active User Account
  • Open Platform Communications
  • CPU Performance Counters
  • Linux Fast Path
  • Host information
  • SSH Keys
  • Account Passwords

NOTES:

The malicious attacker uses the following command to execute arbitrary commands:
exec sh -c {arbitrary command} >/dev/null 2>/dev/null

>/dev/null 2>/dev/null was appended to prevent command outputs/notifications.

This backdoor first checks the following files to steal passwords and private SSH keys:

  • /etc/passwd
  • authorized_keys

The malware monitors the network traffic to receive commands and send back the results through the provided host/port in the received command.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.416.02
FIRST VSAPI PATTERN DATE: 17 Nov 2013
VSAPI OPR PATTERN File: 10.417.00
VSAPI OPR PATTERN Date: 17 Nov 2013

Scan your computer with your Trend Micro product to delete files detected as ELF_FOKIRTOR.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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