Ransom.Win32.CERBER.THKOHBC

November 17, 2023
 Analysis by: Neljorn Nathaniel Aguas
 ALIASES:

Ransom:Win32/Conti.IPA!MTB (MICROSOFT)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted:

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

  TECHNICAL DETAILS

File Size:

251,392 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

01 Nov 2023

Payload:

Drops files, 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 drops the following files:

  • {Malware Path}\{Log Filename} → If the parameter -log {Log Filename} is used
  • {Log Path}\{Log Filename} → If the parameter -log {Log Path}\{Log Filename} is used

It adds the following processes:

  • %System%\cmd.exe /c del {Malware Path}\{Malware Filename} >> NUL
    • Deletes itself after completing its encryption routine.
  • cmd.exe /c %System%\wbem\WMIC.exe shadowcopy where "ID='{Shadowcopy ID}'" delete
    • Deletes shadow copy based on its ID.

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

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

  • hsfjuukjzloqu28oajh727190

Other Details

This Ransomware does the following:

  • By default, it encrypts local files and network shared files.
  • When encrypting network shares it will check if the IP address starts with the following to ensure that it is encrypting local, non-internet, systems:
    • 172.
    • 192.168.
    • 10.
    • 169.

It accepts the following parameters:

  • -p {Path} → Encrypts files in the specified path including subfolders.
  • -b | -b {any string} → Default behavior.
  • -m {all | local | net | backups}
    • local → Encrypts only files in local drives.
    • net → Encrypts only files in network shares.
    • all → Encrypts files in both local drive and network shares (Default behavior).
    • backups → Deletes shadow copies only.
  • -size {chunk mode} → Chunk mode for encrypting large files.
  • -nomutex → Skips creating a mutex.
  • -log {Filename to create} → Creates a log file in {Malware Path} unless a different file path is specified.

It uses Windows Management Instrumentation (WMI) to do the following:

  • SELECT * FROM Win32_ShadowCopy
    • Used to query the list of shadow copies in the system.

Ransomware Routine

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

  • read-me3.txt
  • C3RB3R_LOG.txt

It avoids encrypting files found in the following folders:

  • .
  • ..
  • tmp
  • winnt
  • temp
  • thumb
  • $Recycle.Bin
  • $RECYCLE.BIN
  • System Volume Information
  • Boot
  • Windows
  • Trend Micro
  • perflogs

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

  • .LOCK3D

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

  • read-me3.txt → Dropped in every directory that is not on the exclusion list.

It avoids encrypting files with the following file extensions:

  • .exe
  • .dll
  • .lnk
  • .sys
  • .msi
  • .bat
  • .LOCK3D

It encrypts files using the following encryption methods:
  • Full Encryption:
    • Files with size lower than 1.04 MB
    • Database files with the following file extensions:
      • .4dd
      • .4dl
      • .abcddb
      • .abs
      • .abx
      • .accdb
      • .accdc
      • .accde
      • .accdr
      • .accdt
      • .accdw
      • .accft
      • .adb
      • .ade
      • .adf
      • .adn
      • .adp
      • .alf
      • .arc
      • .ask
      • .bdf
      • .btr
      • .cat
      • .cdb
      • .ckp
      • .cma
      • .cpd
      • .dacpac
      • .dad
      • .dadiagram
      • .daschema
      • .db-shm
      • .db-wal
      • .db2
      • .db3
      • .db
      • .dbc
      • .dbf
      • .dbs
      • .dbt
      • .dbv
      • .dbx
      • .dcb
      • .dct
      • .dcx
      • .ddl
      • .dlis
      • .dp1
      • .dqy
      • .dsk
      • .dsn
      • .dtsx
      • .dxl
      • .eco
      • .ecx
      • .edb
      • .epim
      • .exb
      • .fcd
      • .fdb
      • .fic
      • .fm5
      • .fmp12
      • .fmp
      • .fmpsl
      • .fol
      • .fp3
      • .fp4
      • .fp5
      • .fp7
      • .fpt
      • .frm
      • .gdb
      • .grdb
      • .gwi
      • .hdb
      • .his
      • .hjt
      • .ib
      • .icg
      • .icr
      • .idb
      • .ihx
      • .itdb
      • .itw
      • .jet
      • .jtx
      • .kdb
      • .kdb
      • .kexi
      • .kexic
      • .kexis
      • .lgc
      • .lut
      • .lwx
      • .maf
      • .maq
      • .mar
      • .mas
      • .mav
      • .maw
      • .mdb
      • .mdf
      • .mdn
      • .mdt
      • .mpd
      • .mrg
      • .mud
      • .mwb
      • .myd
      • .ndf
      • .nnt
      • .nrmlib
      • .ns2
      • .ns3
      • .ns4
      • .nsf
      • .nv2
      • .nv
      • .nwdb
      • .nyf
      • .odb
      • .oqy
      • .ora
      • .orx
      • .owc
      • .p96
      • .p97
      • .pan
      • .pdb
      • .pdm
      • .pnz
      • .qry
      • .qvd
      • .rbf
      • .rctd
      • .rod
      • .rodx
      • .rpd
      • .rsd
      • .sas7bdat
      • .sbf
      • .scx
      • .sdb
      • .sdc
      • .sdf
      • .sis
      • .spq
      • .sql
      • .sqlite3
      • .sqlite
      • .sqlitedb
      • .te
      • .temx
      • .tmd
      • .tps
      • .trc
      • .trm
      • .udb
      • .udl
      • .usr
      • .v12
      • .vis
      • .vpd
      • .vvv
      • .wdb
      • .wmdb
      • .wrk
      • .xdb
      • .xld
      • .xmlff
  • Header Encryption:
    • Files with size between 1.04 MB and 5.24 MB
  • Partial Encryption:
    • Files with size greater than 5.24 MB
    • Virtual machine, virtual disk/disc files with the following file extensions:
      • .avdx
      • .avhd
      • .bin
      • .iso
      • .nvram
      • .pvm
      • .qcow2
      • .raw
      • .subvol
      • .vdi
      • .vhd
      • .vhdx
      • .vmcx
      • .vmdk
      • .vmem
      • .vmrs
      • .vmsd
      • .vmsn
      • .vmx
      • .vsv

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.806.01

FIRST VSAPI PATTERN DATE:

08 Nov 2023

VSAPI OPR PATTERN File:

18.807.00

VSAPI OPR PATTERN Date:

09 Nov 2023

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.XXPE50FFF074

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

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.
  • {Malware Path}\{Log Filename}
  • {Log Path}\{Log Filename}
  • {Encrypted Directory}\read-me3.txt

Step 5

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.CERBER.THKOHBC. 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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