RANSOM_LOCKY.TH920

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 modifies the Internet Explorer Zone Settings.

It deletes itself after execution.

It encrypts files with specific file extensions. It drops files as ransom note.

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 drops and executes the following files:

• %Desktop%\ykcol.htm -> ransom note
• %Desktop%\ykcol.bmp -> ransom note, also used as the background image

(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 Ransomware changes the desktop wallpaper by modifying the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%Desktop%\ykcol.bmp"

HKEY_CURRENT_USER\Control Panel\Desktop
TileWallpaper = 0

HKEY_CURRENT_USER\Control Panel\Desktop
WallpaperStyle = 0

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

Web Browser Home Page and Search Page Modification

This Ransomware modifies the Internet Explorer Zone Settings.

Other Details

This Ransomware does the following:

• This ransomware opens the dropped %Desktop%\ykcol.htm which contains the ransom note.
  
• It also opens the dropped %Desktop%\ykcol.bmp which is also the desktop wallpaper that contains the ransom note.
  

It deletes itself after execution.

Ransomware Routine

This Ransomware encrypts files with the following extensions:

• .001
• .002
• .003
• .004
• .005
• .006
• .007
• .008
• .009
• .010
• .011
• .123
• .1cd
• .3dm
• .3ds
• .3fr
• .3g2
• .3gp
• .3pr
• .602
• .7z
• .7zip
• .aac
• .ab4
• .accdb
• .accde
• .accdr
• .accdt
• .ach
• .acr
• .act
• .adb
• .adp
• .ads
• .aes
• .agdl
• .ai
• .aiff
• .ait
• .al
• .aoi
• .apj
• .apk
• .arc
• .arw
• .asc
• .asf
• .asm
• .asp
• .aspx
• .asset
• .asx
• .avi
• .awg
• .back
• .backup
• .backupdb
• .bak
• .bank
• .bat
• .bay
• .bdb
• .bgt
• .bik
• .bin
• .bkp
• .blend
• .bmp
• .bpw
• .brd
• .bsa
• .bz2
• .cdf
• .cdr
• .cdr3
• .cdr4
• .cdr5
• .cdr6
• .cdrw
• .cdx
• .ce1
• .ce2
• .cer
• .cfg
• .cgm
• .cib
• .class
• .cls
• .cmd
• .cmt
• .config
• .contact
• .cpi
• .cpp
• .cr2
• .craw
• .crt
• .crw
• .cs
• .csh
• .csl
• .csr
• .css
• .csv
• .d3dbsp
• .dac
• .das
• .dat
• .db
• .db3
• .db_journal
• .dbf
• .dbx
• .dc2
• .dch
• .dcr
• .dcs
• .ddd
• .ddoc
• .ddrw
• .dds
• .der
• .des
• .design
• .dgc
• .dif
• .dip
• .dit
• .djv
• .djvu
• .dng
• .doc
• .docb
• .docm
• .docx
• .dot
• .dotm
• .dotx
• .drf
• .drw
• .dtd
• .dwg
• .dxb
• .dxf
• .dxg
• .edb
• .eml
• .eps
• .erbsql
• .erf
• .exf
• .fdb
• .ffd
• .fff
• .fh
• .fhd
• .fla
• .flac
• .flf
• .flv
• .flvv
• .forge
• .fpx
• .frm
• .fxg
• .gif
• .gpg
• .gray
• .grey
• .groups
• .gry
• .gz
• .hbk
• .hdd
• .hpp
• .html
• .hwp
• .i
• .ibank
• .ibd
• .ibz
• .idx
• .iif
• .iiq
• .incpas
• .indd
• .iwi
• .j
• .jar
• .java
• .jnt
• .jpe
• .jpeg
• .jpg
• .js
• .kc2
• .kdbx
• .kdc
• .key
• .kpdx
• .kwm
• .l
• .la
• .laccdb
• .lay
• .lay6
• .lbf
• .ldf
• .lit
• .litemod
• .litesql
• .log
• .ltx
• .lua
• .m
• .m2ts
• .m3u
• .m4a
• .m4p
• .m4u
• .m4v
• .mapimail
• .max
• .mbx
• .md
• .mdb
• .mdc
• .mdf
• .mef
• .mfw
• .mid
• .mkv
• .mlb
• .mml
• .mmw
• .mny
• .moneywell
• .mos
• .mov
• .mp3
• .mp4
• .mpeg
• .mpg
• .mrw
• .ms11
• .ms11 (security copy)
• .msg
• .myd
• .myi
• .n64
• .nd
• .ndd
• .ndf
• .nef
• .nk2
• .nop
• .nrw
• .ns2
• .ns3
• .ns4
• .nsd
• .nsf
• .nsg
• .nsh
• .nvram
• .nwb
• .nx2
• .nxl
• .nyf
• .oab
• .obj
• .odb
• .odc
• .odf
• .odg
• .odm
• .odp
• .ods
• .odt
• .ogg
• .oil
• .onetoc2
• .orf
• .ost
• .otg
• .oth
• .otp
• .ots
• .ott
• .p12
• .p7b
• .p7c
• .pab
• .pages
• .paq
• .pas
• .pat
• .pcd
• .pct
• .pdb
• .pdd
• .pdf
• .pef
• .pem
• .pfx
• .php
• .pif
• .pl
• .plc
• .plus_muhd
• .png
• .pot
• .potm
• .potx
• .ppam
• .pps
• .ppsm
• .ppsx
• .ppt
• .pptm
• .pptx
• .prf
• .ps
• .psafe3
• .psd
• .pspimage
• .pst
• .ptx
• .pwm
• .py
• .qba
• .qbb
• .qbm
• .qbr
• .qbw
• .qbx
• .qby
• .qcow
• .qcow2
• .qed
• .r3d
• .raf
• .rar
• .rat
• .raw
• .rb
• .rdb
• .re4
• .rm
• .rtf
• .rvt
• .rw2
• .rwl
• .rwz
• .s3db
• .safe
• .sas7bdat
• .sav
• .save
• .say
• .sch
• .sd0
• .sda
• .sdf
• .sh
• .sldm
• .sldx
• .slk
• .sql
• .sqlite
• .sqlite3
• .sqlitedb
• .sr2
• .srf
• .srt
• .srw
• .st4
• .st5
• .st6
• .st7
• .st8
• .stc
• .std
• .sti
• .stm
• .stw
• .stx
• .svg
• .swf
• .sxc
• .sxd
• .sxg
• .sxi
• .sxm
• .sxw
• .tar
• .tbk
• .tex
• .tga
• .tgz
• .thm
• .tif
• .tiff
• .tlg
• .txt
• .uop
• .uot
• .upk
• .vb
• .vbox
• .vbs
• .vdi
• .vhd
• .vhdx
• .vmdk
• .vmsd
• .vmx
• .vmxf
• .vob
• .wab
• .wad
• .wallet
• .wav
• .wb2
• .wk1
• .wks
• .wma
• .wmv
• .wpd
• .wps
• .x
• .x11
• .x3f
• .xis
• .xlam
• .xlc
• .xlk
• .xlm
• .xlr
• .xls
• .xlsb
• .xlsm
• .xlsx
• .xlt
• .xltm
• .xltx
• .xlw
• .xml
• .y
• .ycbcra
• .yuv
• .zip

It avoids encrypting files with the following strings in their file path:

• _Locky_recover_instructions.txt
• _Locky_recover_instructions.bmp
• System Volume Information
• _HELP_instructions.html
• _HELP_instructions.bmp
• _HELP_instructions.txt
• Program Files (x86)
• Application Data
• Program Files
• $Recycle Bin
• thumbs.db
• AppData
• Windows
• winnt
• Boot
• temp
• tmp

It renames encrypted files using the following names:

• {first 8 characters of ID}--{next 4 characters of ID}--{last 4 characters of ID}--{8 hex characters}--{12 hex characters}.ykcol

It drops the following file(s) as ransom note:

• {Folder containing encrypted files}\ykcol-{4 hex letters}.htm