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Ransom.Win32.COBAIN.A

October 14, 2019
 Analysis by: Warren Adam Sto. Tomas
 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

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:

571,393 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

13 Oct 2019

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 files directory}\__lock_XXX__ -> contains process id of the running malware process and victim ID
  • %ProgramData%\2253bb7a078d5992e3d05911a23a095a7c1507ac3a8abe119587a398c1225833 -> 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 path and file name} 2253bb7a078d5992e3d05911a23a095a7c1507ac3a8abe119587a398c1225833

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random characters} = {malware path and file name} 2253bb7a078d5992e3d05911a23a095a7c1507ac3a8abe119587a398c1225833

Other Details

This Ransomware does the following:

  • It encrypts files found in all removable, fixed, and network drives
  • If a file to be encrypted is found to have an existing process, it will try to terminate this process

Ransomware Routine

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

  • NTUSER.DAT

It avoids encrypting files found in the following folders:

  • Windows Journal
  • Windows Mail
  • Windows Media Player
  • Windows Multimedia Platform
  • Windows NT
  • Windows Photo Viewer
  • Windows Portable Devices
  • Windows Security
  • Windows Sidebar
  • WindowsPowerShell
  • %ProgramData%
  • %Windows%

(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 renames encrypted files using the following names:

  • {encrypted file}.cobain

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

  • {encrypted files directory}\!!!READ_ME!!!.txt

It avoids encrypting files with the following file extensions:

  • .dll
  • .lib
  • .sys
  • page{anything}.sys
  • swap{anything}.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
  • .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
  • .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
  • .spq
  • .sql
  • .sqlite
  • .sqlite3
  • .sqlitedb
  • .sqr
  • .te
  • .teacher
  • .tmd
  • .tps
  • .trc
  • .trm
  • .udb
  • .udl
  • .usr
  • .v12
  • .vis
  • .vpd
  • .vvv
  • .wdb
  • .wmdb
  • .wrk
  • .xdb
  • .xld
  • .xml

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.428.01

FIRST VSAPI PATTERN DATE:

13 Oct 2019

VSAPI OPR PATTERN File:

15.429.00

VSAPI OPR PATTERN Date:

14 Oct 2019

Step 1

Trend Micro products with the XGen technology detect this malware as

[ Learn More ]
Troj.Win32.TRX.XXPE50FFF0

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

Identify and terminate files detected as Ransom.Win32.COBAIN.A

[ 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 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random characters} = {malware path and file name} 2253bb7a078d5992e3d05911a23a095a7c1507ac3a8abe119587a398c1225833
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {random characters} = {malware path and file name} 2253bb7a078d5992e3d05911a23a095a7c1507ac3a8abe119587a398c1225833

Step 6

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 files directory}\__lock_XXX__
  • {encrypted files directory}\!!!READ_ME!!!.txt
  • %ProgramData%\2253bb7a078d5992e3d05911a23a095a7c1507ac3a8abe119587a398c1225833

Step 7

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.COBAIN.A. 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 8

Restore encrypted files from backup.


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