Analysis by: Marvelous Pelin

 ALIASES:

Ransom_WANA (Trend), Win32/Filecoder.WannaCryptor.A (ESET-NOD32), Ransom:Win32/FileCryptor (Microsoft)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware, Downloaded from the Internet

This Trojan 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: 151,552 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 14 Feb 2017
Payload: Connects to URLs/IPs, Encrypts files

Arrival Details

This Trojan 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 Trojan drops the following component file(s):

  • {location of malware}\00000000.key
  • {location of malware}\00000000.res
  • {location of malware}\00000000.dat
  • {location of malware}\taskmsgr.exe - contains ransom note
  • {location of malware}\a.lnk - targets taskmsgr.exe
  • {location of malware}\t1.wry
  • {location of malware}\t2.wry
  • {location of malware}\cg.wy
  • {location of malware}\TaskHost\Tor\taskhosts.exe - copy of tor.exe
  • {folders containing encrypted files}\---HOW_TO_DECRYPT_FILES---.LNK - targets taskmsgr.exe
  • %Desktop%\HOW_TO_DECRYPT_FILES---.LNK - targets taskmsgr.exe

(Note: %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop 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.)

It adds the following processes:

  • taskmsgr.exe
  • taskhosts.exe

It creates the following folders:

  • {location of malware}\TaskHost

Autostart Technique

This Trojan 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

Download Routine

This Trojan accesses the following websites to download files:

  • https://www.{BLOCKED}ject.org/dist/torbrowser/6.0.8/tor-win32-0.2.8.11.zip

It saves the files it downloads using the following names:

  • %Temporary Internet Files%\tor-win32-0.2.8.11.zip

(Note: %Temporary Internet Files% is the Temporary Internet Files folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temporary Internet Files on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Microsoft\Windows\Temporary Internet Files on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), and Windows Server 2008; C:\Users\{user name}\AppData\Local\Microsoft\Windows\INetCache on Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), and Windows Server 2012.)

Other Details

This Trojan 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:

  • 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-gencert.exe
    • Tor\tor.exe
    • Tor\zlib1.dll
  • This ransomware deletes shadow copies by executing the following command:
    • vssadmin.exe Delete Shadows /All /Quiet
  • This ransomware avoids encrypting file with the following strings in their file path:
    • AppData
    • \Users\
    • \ProgramData
    • \Program Files (x86)
    • \Program Files
    • \Windows

NOTES:

This ransomware displays the following window as ransom note:

After clicking the "Start Decrypt" button, it displays the following window:

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 13.222.00
FIRST VSAPI PATTERN DATE: 14 Feb 2017
VSAPI OPR PATTERN File: 13.221.00
VSAPI OPR PATTERN Date: 15 Feb 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

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 6

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.key
  • {location of malware}\00000000.res
  • {location of malware}\00000000.dat
  • {location of malware}\taskmsgr.exe
  • {location of malware}\a.lnk
  • {location of malware}\t1.wry
  • {location of malware}\t2.wry
  • {location of malware}\cg.wy
  • {folders containing encrypted files}\---HOW_TO_DECRYPT_FILES---.LNK
  • %Desktop%\HOW_TO_DECRYPT_FILES---.LNK
  • %Temporary Internet Files%\tor-win32-0.2.8.11.zip

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_WCRY.A. 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 8

Restore encrypted files from backup.


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