RANSOM_CRYPTESLA.YUYAJC

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 the initially executed copy of itself. It gathers information and reports it to its servers.

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 copies of itself into the affected system and executes them:

• %Windows%\{random filename}.exe (with Administrator Privileges)
• %My Documents%\{random filename}.exe (with non-Administrator Privileges)

  (Note: %My Documents% is C:\Users\{user name}\Documents on Windows Vista and above.)

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It drops the following files:

• %My Documents%\recover_file_{random characters}.txt
• Ransom Notes:
  • %Desktop%\_ReCoVeRy_.HTM
  • %Desktop%\_ReCoVeRy_.png
  • %Desktop%\_ReCoVeRy_.TXT
  • %User Profile%\_ReCoVeRy_+{random characters}.html
  • %User Profile%\_ReCoVeRy_+{random characters}.png
  • %User Profile%\_ReCoVeRy_+{random characters}.txt
  • {Folders containing encrypted files}\_ReCoVeRy_+{random characters}.html
  • {Folders containing encrypted files}\_ReCoVeRy_+{random characters}.png
  • {Folders containing encrypted files}\_ReCoVeRy_+{random characters}.txt

(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.)

Autostart Technique

This Trojan creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{4 random characters}-{8 random characters} = "%Windows%\{random filename}.exe" (with Administrator Privileges)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{4 random characters}-{8 random characters} = "%My Documents%\{random filename}.exe" (with non-Administrator Privileges)

Other System Modifications

This Trojan modifies the following file(s):

• It encrypts files and appends the extension .mp3 to them

It adds the following registry keys:

HKEY_CURRENT_USER\Software\zzzsys

HKEY_CURRENT_USER\Software\{Installation ID}

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

HKEY_CURRENT_USER\Software\zzzsys
ID = {Installation ID}

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:

• http://{BLOCKED}edicalcentre.com/wp-content/uploads/wstr.php
• http://{BLOCKED}lizedaccess.co.uk/wp-content/uploads/2015/09/wstr.php
• http://{BLOCKED}stitut.org/wp-content/themes/bstr.php
• http://www.{BLOCKED}aticauno.net/gamma/tmp/bstr.php
• http://www.{BLOCKED}aticauno.net/gamma/tmp/wstr.php
• http://{BLOCKED}our.info/users/28c4fe1/wstr.php

It encrypts files with the following extensions:

• .lvl
• .arch00
• .ntl
• .fsh
• .itdb
• .itl
• .mddata
• .sidd
• .sidn
• .bkf
• .qic
• .bkp
• .bc7
• .bc6
• .pkpass
• .tax
• .gdb
• .qdf
• .t12
• .t13
• .ibank
• .sum
• .sie
• .zip
• .w3x
• .rim
• .psk
• .tor
• .vpk
• .iwd
• .mlx
• .fpk
• .dazip
• .vtf
• .vcf
• .esm
• .blob
• .dmp
• .layout
• .menu
• .kf
• .ncf
• .sid
• .sis
• .ztmp
• .vdf
• .mov
• .fos
• .itm
• .wmo
• .itm
• .map
• .wmo
• .svg
• .cas
• .gho
• .syncdb
• .hkdb
• .hplg
• .hvpl
• .icxs
• .docm
• .wps
• .xls
• .xlsx
• .xlsm
• .xlsb
• .xlk
• .ppt
• .pptx
• .pptm
• .mdb
• .accdb
• .pst
• .dwg
• .dxg
• .wpd
• .rtf
• .wb2
• .pfx
• .p12
• .p7b
• .sb
• .mdbackup
• .xf
• .p7c
• .txt
• .jpeg
• .png
• .css
• .flv
• .m3u
• .desc
• .xxx
• wallet
• .big
• .pak
• .rgss3a
• .epk
• .bik
• .slm
• .lbf
• .sav
• .re4
• .apk
• .bsa
• .ltx
• .forge
• .asset
• .iwi
• .das
• .upk
• .d3dbsp
• .csv
• .wmv
• .avi
• .wma
• .m4a
• .rar
• .mp4
• .sql
• .bak
• .tiff
• .com
• .py
• .js
• .rb
• .litesql
• .litemod
• .7z
• .x3f
• .der
• .cer
• .crt
• .pem
• .odt
• .ods
• .odp
• .odm
• .odc
• .odb
• .doc
• .docx

It deletes the initially executed copy of itself

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

• IP address
• OS version
• installation id (inst_id)
• ID value from the registry HKEY_CURRENT_USER\Software\zzzsys

NOTES:

This malware encrypts files in all fixed, removable, and network drives and shares.

It executes the following command to delete shadow copies:

"C:\Windows\System32\wbem\WMIC.exe" shadowcopy delete /nointeractive

It opens the following ransom notes after encryption: