Analysis by: Henry Alarcon Jr.

ALIASES:

(Microsoft) Ransom:Win32/Sugolock, (ESET-NOD32) Win32/Filecoder.NSU

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

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

  TECHNICAL DETAILS

File Size: 430080 bytes
File Type: EXE
Memory Resident: No
Payload: Displays message/message boxes, Encrypts files

Arrival Details

This Ransomware 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 mutexes to ensure that only one of its copies runs at any one time:

  • qweqwrqafsdgsdfg

Autostart Technique

This Ransomware adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
inf = %User Profile%\DECRYPT.html

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
inf = %User Profile%\DECRYPT.html

Other Details

This Ransomware does the following:

  • Displays the following when executed:


Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • .gdb
  • .ldf
  • .mdf
  • .mdb
  • .pdf
  • .fdb
  • .de
  • .txt
  • .png
  • .jpg
  • .jpeg
  • .bmp
  • .gif
  • .zip
  • .rar
  • .7z
  • .1cd
  • .sql
  • .bak
  • .back
  • .cab
  • .log
  • .ico
  • .old
  • .rtf
  • .lnk
  • .doc
  • .docx
  • .xls
  • .xlsx
  • .tif
  • .vsc
  • .mkv
  • .flac
  • .der
  • .sch
  • .crt
  • .pem
  • .pblix
  • .hbk
  • .epx
  • .dpl
  • .bpl
  • .htm
  • .csv
  • .mp4
  • .mp3
  • .myi
  • .myd
  • .xml
  • .r11
  • .vsl
  • .newdb
  • .srf
  • .pst
  • .ods
  • .dt
  • .cf
  • .erf
  • .html
  • .php
  • .asp
  • .aspx
  • .js
  • .ppt
  • .pptx
  • .java
  • .cpp
  • .css
  • .h
  • .c
  • .jar
  • .swift
  • .os
  • .shtml
  • .less
  • .sass
  • .dat
  • .json
  • .key
  • .avi
  • .3gp
  • .wmv
  • .py
  • .accdb
  • .rmvb
  • .mpg
  • .mov
  • .vob
  • .flv
  • .swf
  • .wma
  • .aac
  • .mmf
  • .amr
  • .m4a
  • .m4r
  • .ogg
  • .mp2
  • .wav
  • .tif
  • .pcx
  • .tga
  • .tiff
  • .odt
  • .dll
  • .exe
  • .rf
  • .glf
  • .msi
  • .vhdx
  • .vhd
  • .bin
  • .vsv
  • .tib
  • .vue
  • .mrimg

It encrypts files found in the following folders:

  • {All Drives}\
  • C:\1a\

It avoids encrypting files with the following strings in their file name:

  • DECRYPT.html
  • {Malware Filename}.exe

It avoids encrypting files with the following strings in their file path:

  • Windows
  • Windows.old
  • ProgramFiles
  • ProgramFiles (x86)
  • All Users
  • Intel
  • $Recycle.Bin
  • Recycle.Bin
  • $RECYCLE.BIN
  • ProgramData

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

  • .GUSv2

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

  • {Encrypted Directory}\DECRYPT.html

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 14.594.04
FIRST VSAPI PATTERN DATE: 29 Oct 2018
VSAPI OPR PATTERN File: 14.595.00
VSAPI OPR PATTERN Date: 30 Oct 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_GUSLOCKER.THAOAIAH

[ 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

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

 
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • inf = "%User Profile%\DECRYPT.html"
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • inf = "%User Profile%\DECRYPT.html"

Step 5

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 Directory}\DECRYPT.html

Step 6

Scan your computer with your Trend Micro product to delete files detected as RANSOM_GUSLOCKER.THAOAIAH. 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 7

Restore encrypted files from backup.


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