Ransom.Win32.MAILTO.THIOFAIA

September 19, 2019
 Modified by: Jay Bradley Nebre
 ALIASES:

Ransom:Win32/Mailto (Microsoft); Ransom-CWall!3D6203DF53FC (McAfee); Trojan.Win32.DelShad.aqi (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt)

 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 deletes itself after execution.

It drops files as ransom note.

  TECHNICAL DETAILS

File Size:

77,824 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

06 Sep 2019

Payload:

Disables services, Terminates processes, Encrypts files, Displays message/message boxes

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 copies of itself into the affected system:

  • %Program Files%\{10 random characters}\{10 random characters}.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000(32-bit), Server 2003(32-bit), XP, Vista(64-bit), 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit) , or C:\Program Files (x86) in Windows XP(64-bit), Vista(64-bit), 7(64-bit), 8(64-bit), 8.1(64-bit), 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following processes:

  • %System%\vssadmin.exe delete shadows /all /quiet

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

It creates the following folders:

  • %Program Files%\{10 random characters}

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000(32-bit), Server 2003(32-bit), XP, Vista(64-bit), 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit) , or C:\Program Files (x86) in Windows XP(64-bit), Vista(64-bit), 7(64-bit), 8(64-bit), 8.1(64-bit), 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It injects itself into the following processes as part of its memory residency routine:

  • explorer.exe

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
{10 random characters} = "%Program Files%\{10 random characters}\{10 random characters}.exe"

Other System Modifications

This Ransomware adds the following registry keys:

HKEY_LOCAL_MACHINE\software\{10 random characters}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\{10 random characters}
{10 random characters} = "{hex values}"

Process Termination

This Ransomware terminates the following services if found on the affected system:

  • Lotus
  • cbvscserv
  • hMailServer
  • backup
  • backup
  • apach
  • firebird
  • ibmiasrw
  • IBM Domino
  • Simply Accounting Database Connection Manager
  • IASJet
  • QB
  • sql
  • sql
  • QuickBooksDB
  • IISADMIN
  • omsad
  • dc32
  • server Administrator
  • wbengine
  • mr2kserv
  • MSExchange
  • ShadowProtectSvc
  • SP4
  • teamviewer
  • MMS
  • AcronisAgent
  • ARSM
  • AcrSch2Svc
  • vsnapvss
  • SPXService
  • StorageCraft ImageManager
  • wrsvc
  • stc_endpt_svc
  • acrsch2svc

It terminates the following processes if found running in the affected system's memory:

  • nslsvice.exe
  • pg
  • nservice.exe
  • cbvscserv
  • ntrtscan.exe
  • cbservi
  • hMailServer
  • IBM
  • bes10
  • black
  • apach
  • bd2
  • db
  • ba
  • be
  • QB
  • oracle
  • wbengine
  • vee
  • postg
  • sage
  • sap
  • b1
  • fdlaunch
  • msmdsrv
  • report
  • msdtssr
  • coldfus
  • cfdot
  • swag
  • swstrtr
  • jetty.exe
  • wrsa.exe
  • team
  • agent
  • store.exe
  • sql
  • sqbcoreservice.exe
  • thunderbird.exe
  • ocssd.exe
  • encsvc.exe
  • excel.exe
  • synctime.exe
  • mspub.exe
  • ocautoupds.exe
  • thebat.exe
  • dbeng50.exe
  • sql
  • mydesktopservice.exe
  • onenote.exe
  • outlook.exe
  • powerpnt.exe
  • msaccess.exe
  • tbirdconfig.exe
  • wordpad.exe
  • ocomm.exe
  • dbsnmp.exe
  • thebat64.exe
  • winword.exe
  • oracle.exe
  • xfssvccon.exe
  • firefoxconfig.exe
  • visio.exe
  • mydesktopqos.exe
  • infopath.exe
  • agntsvc.exe

Other Details

This Ransomware sets the attributes of the following file(s) to Hidden and System:

  • ntuser.dat.log
  • iconcache.db
  • ntuser.ini
  • boot.ini
  • bootmgr
  • bootnxt
  • desktop.ini
  • ntuser.dat
  • autorun.inf
  • ntldr
  • thumbs.db
  • bootsect.bak
  • bootfont.bin

It deletes itself after execution.

Ransomware Routine

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

  • msp
  • bin
  • sys
  • msc
  • mod
  • theme
  • hta
  • shs
  • nomedia
  • diagpkg
  • cab
  • ics
  • msstyles
  • cur
  • drv
  • icns
  • diagcfg
  • dll
  • ocx
  • lnk
  • ico
  • idx
  • ps1
  • mpa
  • cpl
  • icl
  • msu
  • msi
  • nls
  • scr
  • adv
  • 386
  • com
  • hlp
  • rom
  • lock
  • 386
  • wpx
  • ani
  • prf
  • rtp
  • ldf
  • key
  • diagcab
  • cmd
  • spl
  • deskthemepack
  • bat
  • themepack

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

  • system volume information
  • windows.old
  • msocache
  • winnt
  • $windows.~ws
  • perflogs
  • boot
  • windows
  • appdata
  • intel
  • application data
  • programdata
  • $recycle.bin
  • program files
  • google
  • $windows.~bt
  • program files (x86)

It renames encrypted files using the following names:

  • {encrypted file}.mailto[{BLOCKED}ock@{BLOCKED}k.li].{6 random characters}

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

  • {6 random characters}-Readme.txt

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.348.03

FIRST VSAPI PATTERN DATE:

06 Sep 2019

VSAPI OPR PATTERN File:

15.349.00

VSAPI OPR PATTERN Date:

07 Sep 2019

Step 1

Trend Micro products with the XGen technology detect this malware as

[ Learn More ]
Troj.Win32.TRX.XXPE50FFF031

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

Restart in Safe Mode

[ Learn More ]

Step 4

Identify and terminate files detected as Ransom.Win32.MAILTO.THIOFAIA

[ 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 key

[ 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
    • {10 random characters}

Step 6

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
    • {10 random characters}= %Program Files%\{10 random characters}\{10 random characters}.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\c78dd81c87
    • {10 random characters} = {random characters}

Step 7

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %Program Files%\{10 random characters}

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.MAILTO.THIOFAIA. 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 9

Restore encrypted files from backup.


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