RANSOM_LOCKY.DLDTASO

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 modifies the Internet Explorer Zone Settings.

It connects to certain websites to send and receive information. It deletes itself after execution.

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 files:

• {Folder containing encrypted files}\OSIRIS-{4 hex characters}.htm

It drops and executes the following files:

• %User Profile%\DesktopOSIRIS.htm ← ransom note
• %User Profile%\DesktopOSIRIS.bmp ← ransom note, also used as the background image

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

Other System Modifications

This Trojan modifies the following file(s):

• It encrypts files in fixed, removable, RAM disk drives, and network shares.

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Hardware Profiles\0001\Software\
Microsoft\windows\CurrentVersion\
Internet Settings
ProxyEnable = “1”

(Note: The default value data of the said registry entry is 0.)

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

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = “%User Profile%\DesktopOSIRIS.bmp”

(Note: The default value data of the said registry entry is {User preference}.)

HKEY_CURRENT_USER\Control Panel\Desktop
TileWallpaper = “0”

(Note: The default value data of the said registry entry is {User preference}.)

HKEY_CURRENT_USER\Control Panel\Desktop
WallpaperStyle = “0”

(Note: The default value data of the said registry entry is {User preference}.)

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

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Other Details

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

• {BLOCKED}.{BLOCKED}.11.101/checkupdate
• {BLOCKED}.{BLOCKED}.83.189/checkupdate

It encrypts files with the following extensions:

• .001
• .002
• .003
• .004
• .005
• .006
• .007
• .008
• .009
• .01
• .011
• .123
• .602
• .1cd
• .3dm
• .3ds
• .3fr
• .3g2
• .3gp
• .3pr
• .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
• .c
• .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
• .CSV
• .d3dbsp
• .dac
• .das
• .dat
• .db
• .db_journal
• .db3
• .dbf
• .dbx
• .dc2
• .dch
• .dcr
• .dcs
• .ddd
• .ddoc
• .ddrw
• .dds
• .der
• .des
• .design
• .dgc
• .dif
• .dip
• .dit
• .djv
• .djvu
• .dng
• .doc
• .DOC
• .docb
• .docm
• .docx
• .dot
• .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
• .h
• .hbk
• .hdd
• .hpp
• .html
• .hwp
• .ibank
• .ibd
• .ibz
• .idx
• .iif
• .iiq
• .incpas
• .indd
• .iwi
• .jar
• .java
• .jnt
• .jpe
• .jpeg
• .jpg
• .js
• .kc2
• .kdbx
• .kdc
• .key
• .kpdx
• .kwm
• .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
• .MYD
• .MYI
• .n64
• .nd
• .ndd
• .ndf
• .nef
• .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
• .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
• .RTF
• .rvt
• .rw2
• .rwl
• .rwz
• .s3db
• .safe
• .sas7bdat
• .sav
• .save
• .say
• .sch
• .sd0
• .sda
• .sdf
• .sh
• .sldm
• .sldx
• .slk
• .sql
• .sqlite
• .sqlite3
• .SQLITE3
• .sqlitedb
• .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
• .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
• .x11
• .x3f
• .xis
• .xla
• .xlam
• .xlc
• .xlk
• .xlm
• .xlr
• .xls
• .XLS
• .xlsb
• .xlsm
• .xlsx
• .xlt
• .xltm
• .xltx
• .xlw
• .xml
• .ycbcra
• .yuv
• .zip
• wallet.dat

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}.osiris

It does the following:

• It prevents encrypting files containing any of the following strings in its full path name:
  
  • @_HELP_instructions.html
  • _HELP_instructions.bmp
  • _HELP_instructions.txt
  • _Locky_recover_instructions.bmp
  • _Locky_recover_instructions.txt
  • tmp
  • winnt
  • Application Data
  • AppData
  • Program Files (x86)
  • Program Files
  • temp
  • thumbs.db
  • $Recycle.Bin
  • System Volume Information
  • Windows
• It deletes shadow copies by executing following command:
  
  • vssadmin.exe Delete Shadows /Quiet /All

It deletes itself after execution.

NOTES:

The ransomware opens the dropped %User Profile%\DesktopOSIRIS.htm which contains the ransom note.

It also opens the dropped %User Profile%\DesktopOSIRIS.bmp which is also the desktop wallpaper that contains the ransom note.