RANSOM_WCRY.C

 Analysis by: Jennifer Gumban

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 INFORMATION EXPOSURE:

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet


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.

  TECHNICAL DETAILS

File Size:

323,584 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

13 Apr 2017

Payload:

Connects to URLs/IPs, Encrypts files, Displays message/message boxes

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 drops the following file(s)/component(s):

  • {location of malware}\00000000.pky
  • {location of malware}\00000000.eky
  • {location of malware}\00000000.res
  • {location of malware}\!Please Read Me!.txt ← ransomnote
  • {location of malware}\{random numbers}.bat ← creates shortcut
  • {location of malware}\!WannaDecryptor!.exe.lnk
  • {location of malware}\TaskHost\Tor\taskhosts.exe ← copy of tor.exe
  • {location of malware}\t.wry ← encrypted component
  • {location of malware}\c.wry ← contains email, bitcoin address, onion server, & urls
  • {location of malware}\r.wry ← ransomnote
  • {location of malware}\m.wry ← rtf file containing ransom instructions
  • {location of malware}\f.wry ← encrypted files
  • {location of malware}\b.wry ← bmp file used for desktop
  • {location of malware}\u.wry ← tool detected as RANSOM_WCRY.C
  • {location of malware}\!WannaDecryptor!.exe ← tool also detected as RANSOM_WCRY.C
  • {location of malware}\!WannaDecryptor!.bmp ← ransom wallpaper

It adds the following processes:

  • taskhosts.exe

It creates the following folders:

  • {location of malware}\TaskHost

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
Microsoft Task Scheduler = "{location of malware}\{malware filename}.exe" /r 0

Other System Modifications

This Ransomware adds the following registry keys:

HKLM\SOFTWARE\WannaCryptor

HKCU\SOFTWARE\WannaCryptor

It changes the desktop wallpaper by modifying the following registry entries:

HKCU\Control Panel\Desktop
Wallpaper = "{location of malware}\!WannaDecryptor!.bmp"

It sets the system's desktop wallpaper to the following image:

Download Routine

This Ransomware accesses the following websites to download files:

  • https://dist.{BLOCKED}ject.org/torbrowser/6.5.1/tor-win32-0.2.9.10.zip
  • https://www.dropbox.com/s/{BLOCKED}erh1ks/m.rar?dl=1 - hosts - !WannaDecryptor!.exe, detected as RANSOM_WCRY.C
  • https://www.dropbox.com/s/{BLOCKED}zazlyy94/t.zip?dl=1 - hosts Tor archive

Other Details

This Ransomware encrypts files with the following extensions:

  • .123
  • .3dm
  • .3ds
  • .3g2
  • .3gp
  • .602
  • .7z
  • .aes
  • .ai
  • .ARC
  • .asc
  • .asf
  • .asp
  • .avi
  • .backup
  • .bak
  • .bmp
  • .brd
  • .bz2
  • .c
  • .cgm
  • .class
  • .cpp
  • .crt
  • .cs
  • .csr
  • .csv
  • .db
  • .dbf
  • .dch
  • .dif
  • .dip
  • .doc
  • .docb
  • .docm
  • .docx
  • .dot
  • .dotm
  • .dotx
  • .dwg
  • .edb
  • .eml
  • .fla
  • .flv
  • .frm
  • .gif
  • .gpg
  • .gz
  • .h
  • .hwp
  • .ibd
  • .jar
  • .java
  • .jpeg
  • .jpg
  • .js
  • .jsp
  • .key
  • .lay
  • .lay6
  • .ldf
  • .m3u
  • .m4u
  • .max
  • .mdb
  • .mdf
  • .mid
  • .mkv
  • .mml
  • .mov
  • .mp3
  • .mp4
  • .mpeg
  • .mpg
  • .msg
  • .myd
  • .myi
  • .nef
  • .odb
  • .odg
  • .odp
  • .ods
  • .odt
  • .ost
  • .otg
  • .otp
  • .ots
  • .ott
  • .p12
  • .PAQ
  • .pas
  • .pdf
  • .pem
  • .php
  • .pl
  • .png
  • .pot
  • .potm
  • .potx
  • .ppam
  • .pps
  • .ppsm
  • .ppsx
  • .ppt
  • .pptm
  • .pptx
  • .psd
  • .pst
  • .rar
  • .raw
  • .rb
  • .rtf
  • .sch
  • .sh
  • .slk
  • .sln
  • .sql
  • .sqlite3
  • .sqlitedb
  • .stc
  • .std
  • .stw
  • .suo
  • .swf
  • .sxc
  • .sxd
  • .sxm
  • .sxw
  • .tar
  • .tar
  • .tbk
  • .tgz
  • .tif
  • .tiff
  • .txt
  • .uop
  • .uot
  • .vb
  • .vdi
  • .vmdk
  • .vmx
  • .vob
  • .vsd
  • .vsdx
  • .wav
  • .wb2
  • .wk1
  • .wks
  • .wma
  • .wmv
  • .xlc
  • .xlm
  • .xls
  • .xlsb
  • .xlsm
  • .xlsx
  • .xlt
  • .xltm
  • .xltx
  • .xlw
  • .zip

It renames encrypted files using the following names:

  • {original filename and extension}.WCRY

It does the following:

  • Displays the following:




  • !WannaDecryptor!.exe - used for bitcoin payments, ransom intructions and timer, it depends on other components
  • {random numbers}.bat - creates, executes and deletes c.vbs, a script file that creates !WannaDecryptor!.exe.lnk
  • It disables or turns off Windows Error Recovery Screen on Startup using the following command:
    • bcdedit /set {default} bootstatuspolicy ignoreallfailures
  • It disables Startup Repair from running using the following command:
    • bcdedit /set {default} recoveryenabled no
  • It deletes the backup catalog using the following command:
    • wbadmin delete catalog -quiet
  • This ransomware extracts the downloaded zip file in the {location of malware}\TaskHost folder.
  • The downloaded zip file contains the following files:
    • Data\Tor\geoip
    • Data\Tor\geoip6
    • Tor\libeay32.dll
    • Tor\libevent-2-0-5.dll
    • Tor\libevent_core-2-0-5.dll
    • Tor\libevent_extra-2-0-5.dll
    • Tor\libgcc_s_sjlj-1.dll
    • Tor\libssp-0.dll
    • Tor\ssleay32.dll
    • Tor\tor.exe
    • Tor\zlib1.dll
  • This ransomware deletes shadow copies by executing the following command:
    • vssadmin delete shadows /all /quiet
    • wmic shadowcopy delete
  • This ransomware avoids encrypting file with the following strings in their file path:
    • AppData
    • \Users\
    • \ProgramData
    • \Program Files (x86)
    • \Program Files
    • \Windows

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.340.03

FIRST VSAPI PATTERN DATE:

14 Apr 2017

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_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • Microsoft Task Scheduler = "{location of malware}\{malware filename}.exe" /r 0

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
    • WannaCryptor = ""
  • In HKEY_CURRENT_USER\SOFTWARE
    • WannaCryptor = ""

Step 6

Search and delete these folders

[ 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.
  • {location of malware}\TaskHost

Step 7

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.
  • {location of malware}\00000000.pky
  • {location of malware}\00000000.eky
  • {location of malware}\00000000.res
  • {location of malware}\!Please Read Me!.txt
  • {location of malware}\{random numbers}.bat
  • {location of malware}\!WannaDecryptor!.exe.lnk
  • {location of malware}\TaskHost\Tor\taskhosts.exe
  • {location of malware}\t.wry
  • {location of malware}\c.wry
  • {location of malware}\r.wry
  • {location of malware}\m.wry
  • {location of malware}\f.wry
  • {location of malware}\b.wry
  • {location of malware}\!WannaDecryptor!.bmp

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_WCRY.C. 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

Reset your Desktop properties

[ Learn More ]

Step 10

Restore encrypted files from backup.


Did this description help? Tell us how we did.