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Ransom.Win32.COBAIN.F

August 11, 2022
 Analysis by: Jeffrey Francis Bonaobra
 ALIASES:

Ransom:Win32/Hermes.MAK!MTB (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:

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 drops files as ransom note. It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size:

576,641 bytes

File Type:

EXE

File Compression:

UPX

Memory Resident:

Yes

Initial Samples Received Date:

26 May 2022

Payload:

Drops 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 drops the following files:

  • {Encrypted Folders}\__lock_XXX__ → contains process ID of the executed malware process and victim ID
  • %ProgramData%\96288ac666485638d133ea9d874c2f265df81e8ad54896d0232511e39af8f764 → contains victim ID

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit) and XP.)

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
{random characters} = {Malware File Path}\{Malware File Name}.exe 96288ac666485638d133ea9d874c2f265df81e8ad54896d0232511e39af8f764

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random characters} = {Malware File Path}\{Malware File Name}.exe 96288ac666485638d133ea9d874c2f265df81e8ad54896d0232511e39af8f764

Other Details

This Ransomware does the following:

  • It encrypts files found in the following drive types:
    • Fixed Drive
    • Removable Drive
    • Network Drive
  • If a file to be encrypted is found to have an existing process, it will try to terminate this process.

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • {Original File Name}.{Original File Extension}.360

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

  • bootmgr
  • NTUSER.DAT
  • page{anything}.sys
  • swap{anything}.sys

It avoids encrypting files found in the following folders:

  • %ProgramData%
  • %Windows%
  • AnyDesk
  • Common Files
  • Embedded Lockdown Manager
  • Internet Explorer
  • MSBuild
  • Microsoft.NET
  • Oray
  • Reference Assemblies
  • Users\{anything}\Microsoft Help
  • Users\{anything}\Microsoft
  • Users\{anything}\Package Cache
  • Windows Defender
  • Windows Defender Advanced Threat Protection
  • Windows Journal
  • Windows Mail
  • Windows Media Player
  • Windows Multimedia Platform
  • Windows NT
  • Windows Photo Viewer
  • Windows Portable Devices
  • Windows Security
  • Windows Sidebar
  • WindowsPowerShell

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit) and XP.. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

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

  • {Encrypted Folders}\!_INFO.txt
  • %Desktop%\!_INFO.txt

It avoids encrypting files with the following file extensions:

  • .dll
  • .sys
  • .4dd
  • .4dl
  • .accdb
  • .accdc
  • .accde
  • .accdr
  • .accdt
  • .accft
  • .adb
  • .ade
  • .adf
  • .adp
  • .alf
  • .arm
  • .arz
  • .ask
  • .bak
  • .bson
  • .btr
  • .cat
  • .cdb
  • .ckp
  • .cma
  • .cnf
  • .cpd
  • .crypt12
  • .crypt8
  • .crypt9
  • .dacpac
  • .dad
  • .dadiagrams
  • .daschema
  • .db
  • .db-shm
  • .db-wal
  • .db3
  • .dbc
  • .dbf
  • .dbs
  • .dbt
  • .dbv
  • .dbx
  • .dcb
  • .dct
  • .dcx
  • .ddl
  • .dlis
  • .dmp
  • .dp1
  • .dqy
  • .dsk
  • .dsn
  • .dtsx
  • .dxl
  • .eco
  • .ecx
  • .edb
  • .epim
  • .fcd
  • .fdb
  • .fic
  • .fm5
  • .fmp
  • .fmp12
  • .fmpsl
  • .fol
  • .fp3
  • .fp4
  • .fp5
  • .fp7
  • .fpt
  • .frm
  • .gdb
  • .grdb
  • .gwi
  • .hdb
  • .his
  • .ib
  • .ibc
  • .ibd
  • .ibz
  • .idb
  • .ihx
  • .ism
  • .itdb
  • .itw
  • .jet
  • .json
  • .jtx
  • .kdb
  • .kexi
  • .kexic
  • .kexis
  • .ldf
  • .lgc
  • .lwx
  • .maf
  • .maq
  • .mar
  • .marshal
  • .mas
  • .mav
  • .mbk
  • .mdb
  • .mdf
  • .mpd
  • .mrg
  • .mud
  • .mwb
  • .myd
  • .myi
  • .mysql
  • .ndf
  • .nnt
  • .nrmlib
  • .ns2
  • .ns3
  • .ns4
  • .nsf
  • .nv
  • .nv2
  • .nwdb
  • .nyf
  • .odb
  • .opt
  • .oqy
  • .ora
  • .orx
  • .owc
  • .p96
  • .p97
  • .pan
  • .pdb
  • .pdm
  • .phl
  • .pnz
  • .qbquery
  • .qry
  • .qvd
  • .rbf
  • .rctd
  • .rod
  • .rodx
  • .rpd
  • .rsd
  • .rul
  • .sal
  • .sas7bdat
  • .sbf
  • .scx
  • .sdb
  • .sdc
  • .sdf
  • .sis
  • .sld
  • .smd
  • .spq
  • .sql
  • .sqlite
  • .sqlite3
  • .sqlitedb
  • .sqr
  • .te
  • .teacher
  • .tmd
  • .tps
  • .trc
  • .trm
  • .udb
  • .udl
  • .usr
  • .v12
  • .vis
  • .vpd
  • .vvv
  • .wdb
  • .wmdb
  • .wrk
  • .xdb
  • .xld
  • .xmlff

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

17.708.05

FIRST VSAPI PATTERN DATE:

25 Jul 2022

VSAPI OPR PATTERN File:

17.709.00

VSAPI OPR PATTERN Date:

26 Jul 2022

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

    • TROJ.Win32.TRX.XXPE50FFF057

Step 2

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 3

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 4

Restart in Safe Mode

[ Learn More ]

Step 5

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
    • {random characters} = {Malware File Path}\{Malware File Name}.exe 96288ac666485638d133ea9d874c2f265df81e8ad54896d0232511e39af8f764
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random characters} = {Malware File Path}\{Malware File Name}.exe 96288ac666485638d133ea9d874c2f265df81e8ad54896d0232511e39af8f764

Step 6

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 Folders}\__lock_XXX__
  • %ProgramData%\96288ac666485638d133ea9d874c2f265df81e8ad54896d0232511e39af8f764
  • {Encrypted Folders}\!_INFO.txt
  • %Desktop%\!_INFO.txt

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.COBAIN.F. 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 8

Restore encrypted files from backup.


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