RANSOM_ZENIS.THCAFAH

 Analysis by: Michael Jay Villanueva

 ALIASES:

Ransom:MSIL/Zenizozorypt.A (Microsoft); MSIL/Filecoder_Zenis.A!tr (Fortinet); Ransom.Zenis (Malwarebytes)

 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:

Dropped by other malware, Spammed via email


This Ransomware arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It 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:

147,968 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

16 Mar 2018

Payload:

Encrypts files

Arrival Details

This Ransomware arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It 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:

  • ZenisCryptorService

Other System Modifications

This Ransomware adds the following registry entries:

HKEY_CURRENT_USER\Software\ZenisService
Active = 1

Other Details

This Ransomware encrypts files with the following extensions:

  • .3fr
  • .7z
  • .accdb
  • .ai
  • .apk
  • .arch00
  • .arw
  • .asp
  • .aspx
  • .asset
  • .avi
  • .bar
  • .bay
  • .bc6
  • .bc7
  • .big
  • .bik
  • .bkf
  • .bkp
  • .blob
  • .bsa
  • .cas
  • .cdr
  • .cer
  • .cfr
  • .cr2
  • .crt
  • .crw
  • .css
  • .csv
  • .csv
  • .d3dbsp
  • .das
  • .dazip
  • .db0
  • .dba
  • .dbf
  • .dcr
  • .der
  • .desc
  • .dmp
  • .dng
  • .doc
  • .doc
  • .docm
  • .docx
  • .docx
  • .dwg
  • .dxg
  • .epk
  • .eps
  • .erf
  • .esm
  • .ff
  • .flv
  • .forge
  • .fos
  • .fpk
  • .fsh
  • .gdb
  • .gho
  • .hkdb
  • .hkx
  • .hplg
  • .html
  • .hvpl
  • .ibank
  • .icxs
  • .indd
  • .itdb
  • .itl
  • .itm
  • .iwd
  • .iwi
  • .jpe
  • .jpeg
  • .jpg
  • .js
  • .kdb
  • .kdc
  • .kf
  • .layout
  • .lbf
  • .litemod
  • .lrf
  • .ltx
  • .lvl
  • .m2
  • .m3u
  • .m4a
  • .map
  • .mcmeta
  • .mdb
  • .mdb
  • .mdbackup
  • .mddata
  • .mdf
  • .mef
  • .menu
  • .mlx
  • .mov
  • .mp4
  • .mpqge
  • .mrwref
  • .ncf
  • .nrw
  • .ntl
  • .odb
  • .odc
  • .odm
  • .odp
  • .ods
  • .odt
  • .odt
  • .orf
  • .p12
  • .p7b
  • .p7c
  • .pak
  • .pdd
  • .pdf
  • .pef
  • .pem
  • .pfx
  • .php
  • .pk7
  • .pkpass
  • .png
  • .ppt
  • .ppt
  • .pptm
  • .pptx
  • .pptx
  • .psd
  • .psk
  • .pst
  • .ptx
  • .py
  • .qdf
  • .qic
  • .r3d
  • .raf
  • .rar
  • .raw
  • .rb
  • .re4
  • .rgss3a
  • .rim
  • .rofl
  • .rtf
  • .rw2
  • .rwl
  • .sav
  • .sb
  • .sid
  • .sidd
  • .sidn
  • .sie
  • .sis
  • .slm
  • .sln
  • .snx
  • .sql
  • .sql
  • .sr2
  • .srf
  • .srw
  • .sum
  • .svg
  • .syncdb
  • .t12
  • .t13
  • .tax
  • .tor
  • .txt
  • .upk
  • .vcf
  • .vdf
  • .vfs0
  • .vpk
  • .vpp_pc
  • .vtf
  • .w3x
  • .wb2
  • .wma
  • .wmo
  • .wmv
  • .wotreplay
  • .wpd
  • .wps
  • .x3f
  • .xf
  • .xlk
  • .xls
  • .xls
  • .xlsb
  • .xlsm
  • .xlsx
  • .xlsx
  • .xml
  • .xxx
  • .zip
  • .ztmp
  • .wallet

It does the following:

  • It overwrites backup files three (3) times and deletes them afterwards to make it more difficult for the user to restore files from backup. The target backup file extensions are:
    • .win
    • .wbb
    • .w01
    • .v2i
    • .trn
    • .tibkp
    • .sqb
    • .rbk
    • .qic
    • .old
    • .obk
    • .ful
    • .bup
    • .bkup
    • .bkp
    • .bkf
    • .bff
    • .bak
    • .bak2
    • .bak3
    • .edb
    • .stm
  • It terminates processes that contains the following strings if found running on the machine:
    • sql
    • taskmgr
    • regedit
    • backup
  • If the malware's filename is not "iis_agent32.exe", the malware will terminate itself and does not proceed with the encryption and other routine.
  • It deletes shadow copies by executing the following command:
    • vssadmin.exe delete shadows /all /Quiet
    • WMIC.exe shadowcopy delete
    • Bcdedit.exe /set {default} recoveryenabled no
    • Bcdedit.exe /set {default} bootstatuspolicy ignoreallfailures
    • wevtutil.exe cl Application
    • wevtutil.exe cl Security
    • wevtutil.exe cl System

Ransomware Routine

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

  • Windows
  • Program Files
  • ProgramData
  • PerfLogs
  • $Recycle.Bin
  • Microsoft
  • Microsoft Help
  • Microsoft App
  • Certification Kit
  • Windows Defender
  • ESET
  • COMODO
  • Windows NT
  • Windows Kits
  • Windows Mail
  • Windows Media Player
  • Windows Multimedia Platform
  • Windows Phone Kits
  • Windows Phone
  • Silverlight Kits
  • Temp
  • Windows Photo Viewer
  • Windows Protable Devices
  • Windows Slidebar
  • WindowsPowerShell
  • NVIDIA Corporation
  • Microsoft.NET
  • Internet Explorer
  • Kaspersky Lab
  • McAfee
  • Avira
  • spytech software
  • sysconfig
  • Avast
  • Dr.Web
  • Symantec
  • Symantec_Client_Security
  • system volume information
  • AVG
  • Microsoft Shared
  • Common Files
  • Outlook Express
  • Movie Maker
  • Chrome
  • Mozilla Firefox
  • Opera
  • YandexBrowser
  • ntldr
  • Wsus
  • Public

It renames encrypted files using the following names:

  • Zenis-{2 Random Values}.{12 Random Values}

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

  • {Encrypted File Path}\Zenis-Instructions.html

NOTES:

It drops and displays the following ransom note:

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.132.02

FIRST VSAPI PATTERN DATE:

16 Mar 2018

VSAPI OPR PATTERN File:

14.133.00

VSAPI OPR PATTERN Date:

17 Mar 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

Restart in Safe Mode

[ Learn More ]

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_CURRENT_USER\Software\ZenisService
    • Active = 1

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 File Path}\Zenis-Instructions.html

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_ZENIS.THCAFAH. 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 7

Restore encrypted files from backup.


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