Analysis by: Marvelous Pelin
ALIASES:

Ransom:Win32/Locky(Microsoft)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware

This Trojan may be downloaded by other malware/grayware from remote sites.

It connects to certain websites to send and receive information. It deletes the initially executed copy of itself. It gathers information and reports it to its servers. It is capable of encrypting files in the affected system.

  TECHNICAL DETAILS

File Size: 174,592 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 21 Sep 2016
Payload: Connects to URLs/IPs, Modifies files, Encrypts files, Displays graphics/image

Arrival Details

This Trojan may be downloaded by the following malware/grayware from remote sites:

  • TROJ_DAGOZILL.C

Installation

This Trojan drops the following files:

  • {folders containing encrypted files}\_{count of dropped note per folder}_HELP_instructions.html - ransom note

It drops and executes the following files:

  • %Desktop%\_HELP_instructions.html - ransom note
  • %Desktop%\_HELP_instructions.bmp - image used as wallpaper

(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.)

Other System Modifications

This Trojan modifies the following file(s):

  • It renames the encrypted files to {unique ID per victim}-{identifier}.zepto

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

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = %Desktop%\_HELP_instructions.bmp

Other Details

This Trojan connects to the following website to send and receive information:

  • http://{Domain}/data/info.php where {Domain} can be any of the following:
    • {BLOCKED}.{BLOCKED}.154.202
    • {BLOCKED}.{BLOCKED}.52.225
    • {Domain Generated Algorithm}.{ru, info, biz, click, su, work, pl, org, pw, xyz}

It encrypts files with the following extensions:

  • .001
  • .002
  • .003
  • .004
  • .005
  • .006
  • .007
  • .008
  • .009
  • .010
  • .011
  • .123
  • .3dm
  • .3ds
  • .3g2
  • .3gp
  • .602
  • .7z
  • .aes
  • .apk
  • .ARC
  • .asc
  • .asf
  • .asm
  • .asp
  • .asset
  • .avi
  • .bak
  • .bat
  • .bik
  • .bmp
  • .brd
  • .bsa
  • .bz2
  • .c
  • .cgm
  • .class
  • .cmd
  • .cpp
  • .crt
  • .cs
  • .csr
  • .CSV
  • .d3dbsp
  • .das
  • .dat
  • .db
  • .dbf
  • .dch
  • .dif
  • .dip
  • .djv
  • .djvu
  • .DOC
  • .docb
  • .docm
  • .docx
  • .DOT
  • .dotm
  • .dotx
  • .fla
  • .flv
  • .forge
  • .frm
  • .gif
  • .gpg
  • .gz
  • .h
  • .hwp
  • .ibd
  • .iwi
  • .jar
  • .java
  • .jpeg
  • .jpg
  • .js
  • .keywallet
  • .lay
  • .lay6
  • .lbf
  • .ldf
  • .litemod
  • .litesql
  • .ltx
  • .m3u
  • .m4a
  • .m4u
  • .max
  • .mdb
  • .mdf
  • .mid
  • .mkv
  • .mml
  • .mov
  • .mp3
  • .mp4
  • .mpeg
  • .mpg
  • .ms11
  • .MYD
  • .MYI
  • .n64
  • .NEF
  • .odb
  • .odg
  • .odp
  • .ods
  • .odt
  • .onetoc2
  • .otg
  • .otp
  • .ots
  • .ott
  • .p12
  • .PAQ
  • .pas
  • .pdf
  • .pem
  • .php
  • .pl
  • .png
  • .pot
  • .potm
  • .potx
  • .ppam
  • .pps
  • .ppsm
  • .ppsx
  • .PPT
  • .pptm
  • .pptx
  • .psd
  • .pst
  • .qcow2
  • .rar
  • .raw
  • .rb
  • .re4
  • .RTF
  • .sav
  • .sch
  • .sh
  • .sldm
  • .sldx
  • .slk
  • .sql
  • .SQLITE3
  • .SQLITEDB
  • .stc
  • .std
  • .sti
  • .stw
  • .svg
  • .swf
  • .sxc
  • .sxd
  • .sxi
  • .sxm
  • .sxw
  • .tar
  • .tbk
  • .tgz
  • .tif
  • .tiff
  • .txt
  • .uop
  • .uot
  • .upk
  • .vb
  • .vbs
  • .vdi
  • .vmdk
  • .vmx
  • .vob
  • .wallet
  • .wav
  • .wb2
  • .wk1
  • .wks
  • .wma
  • .wmv
  • .xlc
  • .xlm
  • .XLS
  • .xlsb
  • .xlsm
  • .xlsx
  • .xlt
  • .xltm
  • .xltx
  • .xlw
  • .xml
  • .zip

It does the following:

  • It deletes shadow copies by executing the following command:
    • vssadmin.exe Delete Shadows /Quiet /All
  • It requires a specific argument in order to perform its intended routine (ie. 321, 123, 65, etc).
  • It prevents encrypting files containing any of the strings in its full path name:
    • $Recycle.Bin
    • AppData
    • Application Data
    • Program Files
    • Program Files (x86)
    • System Volume Information
    • Temp
    • Thumbs.db
    • Windows
    • winnt
    • Boot

It deletes the initially executed copy of itself

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

  • Language of affected system
  • number of failed encrypted files
  • number of encrypted files
  • OS architecture (if 64bit)
  • victim ID

It is capable of encrypting files in the affected system.

NOTES:

It displays the following ransom notes:

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.790.01
FIRST VSAPI PATTERN DATE: 20 Sep 2016
VSAPI OPR PATTERN File: 12.791.00
VSAPI OPR PATTERN Date: 21 Sep 2016

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_CURRENT_USER\Control Panel\Desktop
    • Wallpaper = %Desktop%\_HELP_instructions.bmp

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.
  • {folders containing encrypted files}\_{count of dropped note per folder}_HELP_instructions.html
  • %Desktop%\_HELP_instructions.html
  • %Desktop%\_HELP_instructions.bmp

Step 6

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