Ransom.Win64.CONTI.AA

April 25, 2023
 Analysis by: Kyle Philippe Yu
 ALIASES:

Gen:Variant.Lazy.326686 (BITDEFENDER)

 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 drops files as ransom note.

  TECHNICAL DETAILS

File Size:

476,160 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

12 Apr 2023

Payload:

Connects to URLs/IPs, 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 drops the following files:

  • %System Root%\CONTI_LOG.txt → If -log enabled is used

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

It adds the following processes:

  • cmd.exe /c %System%\wbem\WMIC\wbem\WMIC.exe shadowcopy where \"ID=’{Shadowcopy ID}’\"delete ← Deletes shadow copies

(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:

  • hsfjuukloqu280ajh727190

Other Details

This Ransomware does the following:

  • It encrypts database storage files by looking for the following strings in their file path:
    • .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
    • .dadiagrams
    • .daschema
    • .db
    • .db2
    • .db3
    • .dbc
    • .dbf
    • .dbs
    • .db-shm
    • .dbt
    • .dbv
    • .db-wal
    • .dbx
    • .dcb
    • .dct
    • .dcx
    • .ddl
    • .dlis
    • .dp1
    • .dqy
    • .dsk
    • .dsn
    • .dtsx
    • .dxl
    • .eco
    • .ecx
    • .edb
    • .epim
    • .exb
    • .fcd
    • .fdb
    • .fic
    • .fm5
    • .fmp
    • .fmp12
    • .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
    • .nv
    • .nv2
    • .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
    • .spg
    • .sql
    • .sqlite
    • .sqlite3
    • .sqlitedb
    • .te
    • .temx
    • .tmd
    • .tps
    • .trc
    • .trm
    • .udb
    • .udl
    • .usr
    • .v12
    • .vis
    • .vpd
    • .vvv
    • .wdb
    • .wdmb
    • .wrk
    • .xdb
    • .xld
    • .xmlff
  • Encrypts network drive
  • It encrypts disk image files by looking for the following file extensions in their file path:
    • .avdx
    • .avhd
    • .bin
    • .iso
    • .nvram
    • .pvm
    • .qcow2
    • .raw
    • .subvol
    • .vdi
    • .vhd
    • .vhdx
    • .vmcx
    • .vmdk
    • .vmem
    • .vmrs
    • .vmsd
    • .vmsn
    • .vmx
    • .vsv
  • When encrypting network shares it will check if the IP address starts with the following to ensure that it is encrypting local and non-internet systems:
    • 172.
    • 192.168.
    • 10.
    • 169.

It accepts the following parameters:

  • -p {Directory} - Encrypts the specific directory first
  • -size {chunk mode}
  • -log {Log File Path}\{Log Filename} - Log output to {Log File Path}\{Log Filename}
  • -nomutex - No mutex will be created
  • -m - {all|local|net|backups}
    • all - combination of net and local
    • local - delete backups and encrypt only locally found drives
    • net - delete backups and encrypt only network shares
    • backups - delete backups

Ransomware Routine

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

  • .EXTEN
  • .exe
  • .dll
  • .lnk
  • .sys
  • .msi
  • readme.txt
  • CONTI_LOG.txt
  • .bat
  • ..

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

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

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

  • .EXTEN

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

  • {Encrypted Directory}\readme.txt

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.436.02

FIRST VSAPI PATTERN DATE:

10 May 2023

VSAPI OPR PATTERN File:

18.437.00

VSAPI OPR PATTERN Date:

11 May 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.XXPE50FFF067

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 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.
  • {Encrypted Directory}\readme.txt
  • %System Root%\CONTI_LOG.txt

Step 5

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win64.CONTI.AA. 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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