Analysis by: Jemimah Mae Molina
ALIASES:

Ransom:Win32/Gerwip (Microsoft); Trojan-Ransom.e (McAfee); Trojan.Win32.Yakes.ywph (Kaspersky); Troj/Ransom-FOO (Sophos); Trojan.Win32.Generic!BT (Sunbelt)

 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: Dropped by other malware, 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 drops files as ransom note.

  TECHNICAL DETAILS

File Size: 930,304 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 04 Aug 2019
Payload: Displays graphics/image, 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 adds the following processes:

  • {Malware Directory}\{Malware File Name}.exe
  • iexplore %Desktop%\{5 random characters}_Entschluesselungs_Anleitung.html → opens ransom note in Internet Explorer
  • vssadmin delete shadows /all /quiet → deletes shadow copies
  • bcdedit /set {default} recoveryenabled no → disables automatic repair
  • bcdedit /set {default} bootstatuspolicy ignoreallfailures → disables Windows error recovery

(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Other System Modifications

This Ransomware sets the system's desktop wallpaper to the following image:

Dropping Routine

This Ransomware drops the following files:

  • %User Temp%\sasi.bmp → used as wallpaper

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Other Details

This Ransomware does the following:

  • It avoids wiping the content of files with the following extensions:
    • .386
    • .adv
    • .ADV
    • .ani
    • .ANI
    • .bat
    • .BAT
    • .bin
    • .BIN
    • .cab
    • .CAB
    • .cmd
    • .CMD
    • .com
    • .COM
    • .cpl
    • .CPL
    • .cur
    • .CUR
    • .deskthemepack
    • .DESKTHEMEPACK
    • .diagcab
    • .DIAGCAB
    • .diagcfg
    • .DIAGCFG
    • .diagpkg
    • .DIAGPKG
    • .dll
    • .DLL
    • .drv
    • .DRV
    • .exe
    • .EXE
    • .hlp
    • .HLP
    • .icl
    • .ICL
    • .icns
    • .ICNS
    • .ico
    • .ICO
    • .ics
    • .ICS
    • .idx
    • .IDX
    • .ldf
    • .lnk
    • .LNK
    • .mod
    • .MOD
    • .mpa
    • .MPA
    • .msc
    • .MSC
    • .msp
    • .MSP
    • .msstyles
    • .MSSTYLES
    • .msu
    • .MSU
    • .nls
    • .NLS
    • .nomedia
    • .NOMEDIA
    • .ocx
    • .OCX
    • .prf
    • .PRF
    • .psl
    • .PSL
    • .rom
    • .ROM
    • .rtp
    • .RTP
    • .scr
    • .SCR
    • .shs
    • .SHS
    • .spl
    • .SPL
    • .sys
    • .SYS
    • .theme
    • .THEME
    • .themepack
    • .THEMEPACK
    • .WPX
    • .lock
    • .LOCK
    • .hta
    • .HTA
    • .msi
    • .MSI
  • It avoids wiping the content of files with the following file names:
    • autorun.inf
    • boot.ini
    • bootfont.bin
    • bootsect.bak
    • desktop.ini
    • iconcache.db
    • ntldr
    • ntuser.dat
    • ntuser.dat.log
    • ntuser.ini
    • bootmgr
    • bootnxt
    • thumbs.db
  • It avoids wiping the content of files found in the following folders:
    • windows
    • recycle.bin
    • mozilla
    • google
    • boot
    • application data
    • appdata
    • program files
    • program files (x86)
    • programme
    • programme (x86)
    • programdata
    • perflogs
    • intel
    • msocache
    • system volume information
  • It appends the following extension to the file name of the files with wiped content:
    • .{5 random characters}

Ransomware Routine

This Ransomware drops the following file(s) as ransom note:

  • {5 random characters}_Entschluesselungs_Anleitung.html

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.280.01
FIRST VSAPI PATTERN DATE: 05 Aug 2019
VSAPI OPR PATTERN File: 15.281.00
VSAPI OPR PATTERN Date: 06 Aug 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

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.ENTSCRYPT.B

[ 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

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.  
  • %User Temp%\sasi.bmp
  • {Encrypted Directory}\{5 random characters}_Entschluesselungs_Anleitung.html

Step 6

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.ENTSCRYPT.B. 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

Reset your Desktop properties

[ Learn More ]

Step 8

Restore encrypted files from backup.

NOTES:
Enabling Volume Shadow Service

  • Run the command prompt (cmd.exe) as administrator.
  • Enable volume shadow service using the following command:

    net start vss

Enabling Windows Error Recovery
  • Run the command prompt (cmd.exe) as administrator.
  • Enable Windows error recovery screen on startup using the following command:

    bcdedit /set {default} bootstatuspolicy displayallfailures

Enabling Startup Repair
  • Run the command prompt (cmd.exe) as administrator.
  • Enable startup repair using the following command:

    bcedit /set {default} recoveryenabled Yes


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