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RANSOM_CESLOCKER.THCOHAH

September 11, 2018
 Analysis by: Robert Nicole Malagad
 ALIASES:

Trojan-Ransom.Win32.Agent.abuo (Kaspersky), Trojan:Win32/Occamy.B (Microsoft)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Spammed via email, Downloaded from the Internet, Dropped by other malware


This Ransomware 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 is capable of encrypting files in the affected system.

It encrypts files with specific file extensions. It drops files as ransom note.

  TECHNICAL DETAILS

File Size:

970,752 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

06 Mar 2018

Payload:

Collects system information, Encrypts files,, Connects to URLs/IPs

Arrival Details

This Ransomware 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 Ransomware adds the following processes:

  • %Program Files%\Internet Explorer\iexplore.exe" -nohome ← Command to set the Internet Explorer's home page disabled

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), 7 (32-bit), and 8 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), 7 (64-bit), and 8 (64-bit).)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • HhQVyWJgqt

Information Theft

This Ransomware gathers the following data:

  • User Name
  • System Processor
  • System Locale ID
  • OS Version
  • System Language

Other Details

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

  • {BLOCKED}.{BLOCKED}.125.1-176.10.125.254
  • {BLOCKED}.{BLOCKED}.126.1-176.10.126.254
  • {BLOCKED}.{BLOCKED}.127.1-176.10.127.254

It does the following:

  • It skips to encrypt the following paths:
    • $recycle.bin
    • systemvolumeinformation
    • temporaryinternetfiles
    • programfiles
    • programdata
    • programfiles(x86)
    • windows
    • microsoft
    • appdata
    • localsettings
    • recycler
    • msocache

It is capable of encrypting files in the affected system.

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • .1cd
  • .3ds
  • .3gp
  • .accdb
  • .ai
  • .ape
  • .asp
  • .aspx
  • .bc6
  • .bc7
  • .bmp
  • .cdr
  • .cer
  • .cfg
  • .cfgx
  • .cpp
  • .cr2
  • .crt
  • .crw
  • .csr
  • .csv
  • .dbf
  • .dbx
  • .dcr
  • .dfx
  • .dib
  • .djvu
  • .doc
  • .docm
  • .docx
  • .dwg
  • .dwt
  • .dxf
  • .dxg
  • .eps
  • .htm
  • .html
  • .ibank
  • .indd
  • .jfif
  • .jpe
  • .jpeg
  • .jpg
  • .kdc
  • .kwm
  • .max
  • .md
  • .mdb
  • .mdf
  • .odb
  • .odc
  • .odm
  • .odp
  • .ods
  • .odt
  • .orf
  • .p12
  • .p7b
  • .p7c
  • .pdf
  • .pef
  • .pem
  • .pfx
  • .php
  • .pl
  • .png
  • .pps
  • .ppt
  • .pptm
  • .pptx
  • .psd
  • .pst
  • .pub
  • .pwm
  • .py
  • .qbb
  • .qbw
  • .raw
  • .rtf
  • .sln
  • .sql
  • .sqlite
  • .svg
  • .tif
  • .tiff
  • .txt
  • .vcf
  • .wallet
  • .wpd
  • .xls
  • .xlsm
  • .xlsx
  • .xml

It appends the following extension to the file name of the encrypted files:

  • .{Random Characters}

It drops the following file(s) as ransom note:

  • {Encrypted Folder}\=_HOW_TO_FIX_{Random Characters}.html
  • {Encrypted Folder}\=_HOW_TO_FIX_{Random Characters}.txt
  • {Encrypted Fodler}\=_HOW_TO_FIX_{Random Characters}.url

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.116.02

FIRST VSAPI PATTERN DATE:

08 Mar 2018

VSAPI OPR PATTERN File:

14.117.00

VSAPI OPR PATTERN Date:

09 Mar 2018

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

Identify and terminate files detected as RANSOM_CESLOCKER.THCOHAH

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

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.  
  • {Encrypted Folder}\=_HOW_TO_FIX_{Random Characters}.html
  • {Encrypted Folder}\=_HOW_TO_FIX_{Random Characters}.txt
  • {Encrypted Fodler}\=_HOW_TO_FIX_{Random Characters}.url

Step 5

Scan your computer with your Trend Micro product to delete files detected as RANSOM_CESLOCKER.THCOHAH. 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 the following Trend Micro Support pages for more information:

Step 6

Restore encrypted files from backup.


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