RANSOM_SIGRUN.THEBAAH

 Analysis by: John Donnie Celestre
 Modified by: Noel Anthony Llimos

 ALIASES:

Trojan-Ransom.Win32.Cryptor.bsj (Kaspersky), Mal/EncPk-MP (Sophos_Lite)

 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

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 encrypts files with specific file extensions.

  TECHNICAL DETAILS

File Size:

48,640 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

21 May 2018

Payload:

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:

  • %All Users Profile%\{Random Characters}.lock
  • {Encrypted Directory}\RESTORE-SIGRUN.html
  • {Encrypted Directory}\RESTORE-SIGRUN.txt

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It adds the following processes:

  • iexplore.exe /C iexplore.exe SCODEF:3124 CREDAT:14337 <- Used to pop up the ransom page of the malware
  • %Program Files%\Internet Explorer\iexplore.exe -nohome <- Used to Disable the homepage of Internet Explorer

(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)

It leaves text files that serve as ransom notes containing the following:

Other System Modifications

This Ransomware adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\Valkyrie\
data
public = {Hex Values}

HKEY_CURRENT_USER\Software\Valkyrie\
data
KeyData = {Hex Values}

Other Details

This Ransomware does the following:

  • It deletes shadow copies by executing the following command:
    • "cmd.exe" /c wmic shadowcopy delete
  • It deletes the initialized copy of itself by executing the following commands:
    • "cmd.exe" /c timeout -c 5 & del "{Malware File Path}\{Malware File Name}" /f /q
  • It avoids encrypting files with the following extensions:
    • .admin
    • .ani
    • .bat
    • .cab
    • .cmd
    • .cpl
    • .cur
    • .diagcab
    • .diagpkg
    • .dll
    • .drv
    • .exe
    • .hlp
    • .icl
    • .icns
    • .ico
    • .ics
    • .idx
    • .key
    • .ldf
    • .lnk
    • .mod
    • .mpa
    • .msc
    • .msp
    • .msstyles
    • .msu
    • .nomedia
    • .ocx
    • .prf
    • .rom
    • .rtp
    • .scr
    • shs
    • .sigrun
    • .sigrun_key
    • .spl
    • .sys
    • .theme
    • .themepack
  • It displays the following ransom note in Internet Explorer:

It deletes itself after execution.

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • .DIC
  • .acl
  • .acrodata
  • .avi
  • .bak
  • .blog
  • .bmp
  • .btapp
  • .cfg
  • .conf
  • .contact
  • .crl
  • .css
  • .dat
  • .data
  • .db
  • .doc
  • .docx
  • .dot
  • .dotm
  • .dotx
  • .etl
  • .flv
  • .gif
  • .glox
  • .html
  • .info
  • .ini
  • .jpg
  • .js
  • .json
  • .jsonlz4
  • .m4a
  • .metadata
  • .metadata-v
  • .mkv
  • .mp3
  • .mp4
  • .mpt
  • .ods
  • .ods
  • .odt
  • .one
  • .ots
  • .pdf
  • .png
  • .ppt
  • .pptx
  • .pst
  • .rdf
  • .rtf
  • .sdi
  • .searchconnector-ms
  • .sqlite
  • .srs
  • .swf
  • .thmx
  • .timestamp
  • .url
  • .wim
  • .wmv
  • .wtv
  • .xml

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

  • Bootfont.bin
  • NTDETECT.COM
  • RESTORE-SIGRUN.txt
  • autorun.inf
  • boot.ini
  • bootsect.bak
  • desktop.ini
  • iconcache .db
  • ntldr
  • ntuser.dat
  • ntuser.dat.log
  • thumbs.db

It avoids encrypting files found in the following folders:

  • %All Users Profile%
  • %Program Files%
  • %ProgramData%
  • %Windows%
  • Boot
  • IETldCache
  • Local Settings
  • Tor Browser

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.. %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData in Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

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

  • .sigrun

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.264.03

FIRST VSAPI PATTERN DATE:

20 May 2018

VSAPI OPR PATTERN File:

14.265.00

VSAPI OPR PATTERN Date:

21 May 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

Identify and terminate files detected as RANSOM_SIGRUN.THEBAAH

[ 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 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.  
  • %All Users Profile%\{Random Characters}.lock
  • {Encrypted Directory}\RESTORE-SIGRUN.html
  • {Encrypted Directory}\RESTORE-SIGRUN.txt

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.

  • HKEY_CURRENT_USER\Software\Valkyrie\data
  • public = {Hex Values}
  • HKEY_CURRENT_USER\Software\Valkyrie\data
  • KeyData = {Hex Values}

Step 6

Scan your computer with your Trend Micro product to delete files detected as RANSOM_SIGRUN.THEBAAH. 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 7

Restore encrypted files from backup.


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