Threat Encyclopedia

TROJ_CRYPAURA.A

Publish date: November 21, 2014

ANALYSIS BY

Rika Joi Gregorio


ALIASES:

Trojan-Ransom.Win32.Aura.aq(Kaspersky), Trojan-Ransom.Win32.Aura(Ikarus)

PLATFORM:

Windows

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

  • Threat Type:Trojan

  • Destructiveness:No

  • Encrypted: Yes

  • In the wild: Yes

OVERVIEW

Infection Channel:

Downloaded from the Internet, Spammed via email


This ransomware variant uses the text ebola as part of the extension name that it appends on the file that it encrypts.

To get a one-glance comprehensive view of the behavior of this Trojan, refer to the Threat Diagram shown below.

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It connects to certain websites to send and receive information. It deletes itself after execution.

TECHNICAL DETAILS

File Size:

3,334,144 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

21 Nov 2014

Payload:

Connects to URLs/IPs, Displays graphics/image, Encrypts files

Arrival Details

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It 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 files:

  • %Application Data%\ebola.bmp - ransom message
  • %Start Menu%\Programs\Startup\ebola.bmp - ransom message (for Windows Vista and higher)
  • %User Startup%\ebola.bmp - ransom message (for Windows XP and lower)

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %Start Menu% is the Start Menu folder, where it usually is C:\Documents and Settings\{user name}\Start Menu on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

Autostart Technique

This Trojan drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %Start Menu%\Programs\Startup\{malware file name}.exe - for Windows Vista and higher
  • %User Startup%\{malware file name}.exe - for Windows XP and lower

(Note: %Start Menu% is the Start Menu folder, where it usually is C:\Documents and Settings\{user name}\Start Menu on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

Information Theft

This Trojan gathers the following data:

  • Computer name
  • Machine GUID

Other Details

This Trojan connects to the following website to send and receive information:

  • http://{BLOCKED}rotect.info/donbass/script.php
  • http://{BLOCKED}rotect.info/lugansk/script.php

It encrypts files with the following extensions:

  • 1cd
  • 3gp
  • 7z
  • arj
  • avi
  • bak
  • cdr
  • cer
  • cpt
  • csv
  • db3
  • dbf
  • doc
  • docx
  • dt
  • dwg
  • gzip
  • jpeg
  • jpg
  • key
  • m2v
  • mdb
  • mkv
  • mov
  • mpeg
  • ods
  • odt
  • pdf
  • ppsx
  • pptx
  • ppt
  • pwm
  • rar
  • raw
  • rtf
  • temp
  • tib
  • wab
  • xls
  • xlsx
  • zip

It renames encrypted files using the following names:

  • {original file name and extension}.id-{id}_help@antivirusebola.com

It deletes itself after execution.

NOTES:

This Trojan may display the following message at every startup:

It traverses the following drives to encrypt files:

  • c:\
  • d:\
  • e:\
  • f:\
  • g:\
  • h:\
  • i:\
  • j:\
  • k:\
  • l:\
  • m:\
  • n:\
  • o:\
  • q:\
  • r:\
  • s:\
  • t:\
  • u:\
  • v:\
  • w:\
  • x:\
  • y:\
  • z:\

It avoids encrypting files located in the following folders:

  • Program Data
  • Program Files
  • Program Files (x86)
  • Windows

SOLUTION

Minimum Scan Engine:

9.700

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Search and delete these files

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %Application Data%\ebola.bmp
  • %Start Menu%\Programs\Startup\ebola.bmp - for Windows Vista and higher
  • %User Startup%\ebola.bmp - for Windows XP and lower

Step 4

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

NOTES:

Restore the encrypted files by this malware from backup. Note that the encrypted files have the extension .id-{id}_help@antivirusebola.com.


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