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RANSOM_WALTRIX.YUYALA

May 31, 2016
 Analysis by: Janus Agcaoili
 ALIASES:

Ransom:Win32/Exxroute.B (Microsoft), Trojan-Ransom.Win32.CryptXXX.aan (Kaspersky), W32/CryptXXX.AAN!tr (Fortinet)

 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:

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.

It terminates itself if it detects it is being run in a virtual environment. It gathers information and reports it to its servers.

  TECHNICAL DETAILS

File Size:

258,048 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

23 May 2016

Payload:

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

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 file(s)/component(s):

  • %All Users Profile%\{unique ID}.key
  • %All Users Profile%\Z - deleted afterwards; contains installation date of the malware
  • {folders containing encrypted files}\!Recovery_{unique ID}.bmp - image used as wallpaper
  • {folders containing encrypted files}\!Recovery_{unique ID}.html - ransom note
  • {folders containing encrypted files}\!Recovery_{unique ID}.txt - ransom note

(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:

  • copy of the file that executed the DLL ransomware (such as legitimate rundll32.exe or regsvr32.exe) named as:
    • {malware path}\svchost.exe
  • executes svchost.exe {malware}.dll, MS11{number}

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • {first 5 characters from the unique ID}

Autostart Technique

This Trojan drops the following files:

  • %User Startup%\{unique ID}.lnk

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
TileWallpaper = "0"

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "{random}\{unique ID}.bmp"

Other Details

This Trojan encrypts files with the following extensions:

  • .3DM
  • .3DS
  • .3G2
  • .3GP
  • .7Z
  • .ACCDB
  • .AES
  • .AI
  • .AIF
  • .APK
  • .APP
  • .ARC
  • .ASC
  • .ASF
  • .ASM
  • .ASP
  • .ASPX
  • .ASX
  • .AVI
  • .BMP
  • .BRD
  • .BZ2
  • .C
  • .CER
  • .CFG
  • .CFM
  • .CGI
  • .CGM
  • .CLASS
  • .CMD
  • .CPP
  • .CRT
  • .CS
  • .CSR
  • .CSS
  • .CSV
  • .CUE
  • .DB
  • .DBF
  • .DCH
  • .DCU
  • .DDS
  • .DIF
  • .DIP
  • .DJV
  • .DJVU
  • .DOC
  • .DOCB
  • .DOCM
  • .DOCX
  • .DOT
  • .DOTM
  • .DOTX
  • .DTD
  • .DWG
  • .DXF
  • .EML
  • .EPS
  • .FDB
  • .FLA
  • .FLV
  • .FRM
  • .GADGET
  • .GBK
  • .GBR
  • .GED
  • .GIF
  • .GPG
  • .GPX
  • .GZ
  • .H
  • .H
  • .HTM
  • .HTML
  • .HWP
  • .IBD
  • .IBOOKS
  • .IFF
  • .INDD
  • .JAR
  • .JAVA
  • .JKS
  • .JPG
  • .JS
  • .JSP
  • .KEY
  • .KML
  • .KMZ
  • .LAY
  • .LAY6
  • .LDF
  • .LUA
  • .M
  • .M3U
  • .M4A
  • .M4V
  • .MAX
  • .MDB
  • .MDF
  • .MFD
  • .MID
  • .MKV
  • .MML
  • .MOV
  • .MP3
  • .MP4
  • .MPA
  • .MPG
  • .MS11
  • .MSI
  • .MYD
  • .MYI
  • .NEF
  • .NOTE
  • .OBJ
  • .ODB
  • .ODG
  • .ODP
  • .ODS
  • .ODT
  • .OTG
  • .OTP
  • .OTS
  • .OTT
  • .P12
  • .PAGES
  • .PAQ
  • .PAS
  • .PCT
  • .PDB
  • .PDF
  • .PEM
  • .PHP
  • .PIF
  • .PL
  • .PLUGIN
  • .PNG
  • .POT
  • .POTM
  • .POTX
  • .PPAM
  • .PPS
  • .PPSM
  • .PPSX
  • .PPT
  • .PPTM
  • .PPTX
  • .PRF
  • .PRIV
  • .PRIVAT
  • .PS
  • .PSD
  • .PSPIMAGE
  • .PY
  • .QCOW2
  • .RA
  • .RAR
  • .RAW
  • .RM
  • .RSS
  • .RTF
  • .SCH
  • .SDF
  • .SH
  • .SITX
  • .SLDX
  • .SLK
  • .SLN
  • .SQL
  • .SQLITE
  • .SQLITE
  • .SRT
  • .STC
  • .STD
  • .STI
  • .STW
  • .SVG
  • .SWF
  • .SXC
  • .SXD
  • .SXI
  • .SXM
  • .SXW
  • .TAR
  • .TBK
  • .TEX
  • .TGA
  • .TGZ
  • .THM
  • .TIF
  • .TIFF
  • .TLB
  • .TMP
  • .TXT
  • .UOP
  • .UOT
  • .VB
  • .VBS
  • .VCF
  • .VCXPRO
  • .VDI
  • .VMDK
  • .VMX
  • .VOB
  • .WAV
  • .WKS
  • .WMA
  • .WMV
  • .WPD
  • .WPS
  • .WSF
  • .XCODEPROJ
  • .XHTML
  • .XLC
  • .XLM
  • .XLR
  • .XLS
  • .XLSB
  • .XLSM
  • .XLSX
  • .XLT
  • .XLTM
  • .XLTX
  • .XLW
  • .XML
  • .YUV
  • .ZIP
  • .ZIPX

It renames encrypted files using the following names:

  • {original file name.file extension}.crypt

It terminates itself if it detects it is being run in a virtual environment.

It does the following:

  • It checks if it is being run in a virtual environment by:
    • querying the registry entry:
       HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\CentralProcessor\0\ProcessorNameString
    • checks mouse activity

It gathers the following information and reports it to its servers:

  • It reports infection status and unique ID to {BLOCKED}.{BLOCKED}.187.64:443

  SOLUTION

Minimum Scan Engine:

9.800

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

Restore this modified 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_CURRENT_USER\Control Panel\Desktop
    • Wallpaper = "{random}\{unique ID}.bmp"
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • TileWallpaper = "0"

Step 5

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.
  • %User Startup%\{unique ID}.lnk
  • %All Users Profile%\{unique ID}.key
  • %All Users Profile%\Z
  • {folders containing encrypted files}\!Recovery_{unique ID}.html
  • {folders containing encrypted files}\!Recovery_{unique ID}.bmp
  • {folders containing encrypted files}\!Recovery_{unique ID}.txt

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_WALTRIX.YUYALA. 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 7

Restore encrypted files from backup.


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