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ELF_CRYPTOR.A

November 11, 2015
 Analysis by: David John Agni
 ALIASES:

ELF/Filecoder.A (F-Prot), Trojan-Ransom.Linux.Cryptor.a (Kaspersky), Linux/Ransm-C (Sophos)

 PLATFORM:

Unix, Linux

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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.

  TECHNICAL DETAILS

File Size:

278,198 bytes

File Type:

ELF

Memory Resident:

Yes

Initial Samples Received Date:

09 Nov 2015

Payload:

Encrypts files

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 non-malicious files:

  • README_FOR_DECRYPT.txt - to all folders where files are encrypted.

Other Details

This Trojan encrypts files with the following extensions:

  • .php
  • .html
  • .tar
  • .gz
  • .sql
  • .js
  • .css
  • .pdf
  • .tgz
  • .war
  • .jar
  • .java
  • .class
  • .ruby
  • .rar
  • .zip
  • .db
  • .7z
  • .doc
  • .pdf
  • .xls
  • .properties
  • .xml
  • .jpg
  • .jpeg
  • .png
  • .gif
  • .mov
  • .avi
  • .wmv
  • .mp3
  • .mp4
  • .wma
  • .aac
  • .wav
  • .pem
  • .pub
  • .docx
  • .apk
  • .exe
  • .dll
  • .tpl
  • .psd
  • .asp
  • .phtml
  • .aspx
  • .csv

It opens the following files:

  • ./readme.crypto - Contains data to be written in README_FOR_DECRYPT.txt
  • ./index.crypto

It renames encrypted files using the following names:

  • {Filename}.encrypted

NOTES:

It initially encrypt files found in the following directories:

  • /home
  • /root
  • /var/lib/mysql
  • /var/www
  • /etc/nginx
  • /etc/apache2
  • /var/log

It avoids encrypting files within the following directories:

  • /
  • /root/.ssh

  SOLUTION

Minimum Scan Engine:

9.800

VSAPI OPR PATTERN File:

12.141.00

VSAPI OPR PATTERN Date:

10 Nov 2015

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