Analysis by: Jeanne Jocson

 PLATFORM:

Windows

 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: Downloaded from the Internet, Dropped by other malware

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 deletes itself after execution.

  TECHNICAL DETAILS

File Size: 1,293,824 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 16 Aug 2016
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 leaves text files that serve as ransom notes containing the following:

  • 당신의 파일이 암호화 되었습니다.{password}

Dropping Routine

This Trojan drops the following files:

  • %Desktop%\ReadMe.txt -Serves as ransom note

(Note: %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop in 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.)

Other Details

This Trojan encrypts files with the following extensions:

  • .txt
  • .doc
  • .docx
  • .xls
  • .xlsx
  • .ppt
  • .pptx
  • .odt
  • .jpg
  • .png
  • .csv
  • .sql
  • .mdb
  • .hwp
  • .pdf
  • .php
  • .asp
  • .aspx
  • .html
  • .xml
  • .psd

It renames encrypted files using the following names:

  • {filename of encrypted file}.암호화됨-translated as "encrypted"

It does the following:

  • It encrypts the files found in the following directories:
    • %Desktop%\
    • %Desktop%\{subfolders}\

(Note: %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop in 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.)

It deletes itself after execution.

NOTES:

It displays the following as Ransom Note:

The text is translated as follows:

Your files have been encrypted.
Go to the following address:
You can check the information for decryption:
http://{BLOCKED}t225dfs5mom.{BLOCKED}n.city
Go to the site above. TOR browser is required

As of this writing the said site is already inaccessible.

It also have the following capabilities which have not been used upon its execution:

  • Send the generated password to the following URL:
    • https://www.{BLOCKED}e.com/hidden-tear/write.php?info={random} {password}
  • Displays the following:

    식별아이디: ADEFE4B1: 49A860F8: 5D9CF787: B15772D6
    자세한 설명은 아래 링크 참조
    1 - http://{BLOCKED}ao5mom.onion.to
    2 - http://{BLOCKED}5ao5mom.onion.city
    1 - 다운로드 토르브라우져: http://www.torproject.org/projects/torbrowser.html.en
    토르브라우져 다운로드후 아래주소로 접속
    http://t352fwt225ao5mom.onion
    식별아이디를 이용하여 결제
    자세한 내용은 홈페이지에있습니다.

The text is translated as follows:

Identification ID: ADEFE4B1: 49A860F8: 5D9CF787: B15772D6
See the link below for further explanation
1 - http://{BLOCKED}25ao5mom.onion.to
2 - http://t352fwt225ao5mom.onion.to
1 - Download Tor Browser: http://www.torproject.org/projects/torbrowser.html.en
Connect to the following address after downloading Tor Browser
http: //t352fwt225ao5mom.onion
Payments using the identification ID
Details are on the website.

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.720.05
FIRST VSAPI PATTERN DATE: 17 Aug 2016
VSAPI OPR PATTERN File: 12.721.00
VSAPI OPR PATTERN Date: 18 Aug 2016

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 this file

[ 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.  
  • %Desktop%\ReadMe.txt

Step 4

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

Step 5

Restore encrypted files from backup.


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