RANSOM_CRYPTESLA.YUYAHT

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 does not have any propagation routine.

It does not have any backdoor routine.

It modifies the Internet Explorer Zone Settings.

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

• %Application Data%\{random characters}.exe

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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 mutexes to ensure that only one of its copies runs at any one time:

• __sys_234238233295

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
dsfgsdf-67897869 = "%Application Data%\{random characters}.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
dsfgsdf-67897869 = "%Application Data%\{random characters}.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\xxxsys

HKEY_CURRENT_USER\Software\{Installation ID}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnabledLinkConnections = "1"

HKEY_CURRENT_USER\Software\{Installation ID}
data = {encryption information}

HKEY_CURRENT_USER\Software\xxxsys
ID = {Installation ID}

Propagation

This Trojan does not have any propagation routine.

Backdoor Routine

This Trojan does not have any backdoor routine.

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Dropping Routine

This Trojan drops the following files:

• %User Profile%\Documents\recover_file_{random letters}.txt
• %Desktop%\help_recover_instructions.HTM
• %Desktop%\help_recover_instructions.png
• %Desktop%\help_recover_instructions.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.. %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 Details

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

• http://{BLOCKED}pourisrael.com/modules/mod_speedup/mzsys.php
• http://{BLOCKED}ricoop.net/tmp/mzsys.php
• http://{BLOCKED}eerleaders.fr/modules/mod_cmscore/mzsys.php
• http://{BLOCKED}b.net/templates/assets/email_tmpl/uploads/mzsys.php
• http://{BLOCKED}dehaan.be/modules/mod_cmscore/mzsys.php
• http://{BLOCKED}ft.com/templates/sj_icenter/html/mod_k2_content/Default/mzsys.php

It encrypts files with the following extensions:

• .3fr
• .7z
• .accdb
• .ai
• .amp
• .apk
• .arch00
• .arw
• .asset
• .avi
• .bar
• .bay
• .bc6
• .bc7
• .big
• .bik
• .bkf
• .bkp
• .blob
• .bsa
• .cas
• .cdr
• .cer
• .cfr
• .cr2
• .crt
• .crw
• .css
• .csv
• .d3dbsp
• .das
• .dazip
• .db0
• .dba
• .dbf
• .dcr
• .der
• .desc
• .dmp
• .dng
• .doc
• .docm
• .docx
• .dwg
• .dxg
• .epk
• .eps
• .erf
• .esm
• .ff
• .flv
• .forge
• .fos
• .fpk
• .fsh
• .gdb
• .gho
• .hkdb
• .hkx
• .hplg
• .hvpl
• .ibank
• .icxs
• .indd
• .itd
• .itdb
• .itl
• .itm
• .iwd
• .iwi
• .jpeg
• .jpg
• .js
• .kdb
• .kdc
• .kf
• .layout
• .lbf
• .litemod
• .lrf
• .ltx
• .lvl
• .m2
• .m3u
• .m4a
• .mcmeta
• .mdb
• .mdbackup
• .mdd
• .mddata
• .mdf
• .mef
• .menu
• .mlx
• .mov
• .mp4
• .mpqge
• .mrwref
• .ncf
• .nrw
• .ntl
• .odb
• .odc
• .odm
• .odp
• .ods
• .odt
• .orf
• .p12
• .p7b
• .p7c
• .pak
• .pdd
• .pdf
• .pef
• .pem
• .pfx
• .pkb
• .pkpass
• .png
• .ppt
• .pptm
• .pptx
• .psd
• .psk
• .pst
• .ptx
• .py
• .qdf
• .qic
• .r3d
• .raf
• .rar
• .raw
• .rb
• .re4
• .rgss3a
• .rim
• .rofl
• .rtf
• .rw2
• .rwl
• .sav
• .sb
• .sid
• .sidd
• .sidn
• .sie
• .sis
• .slm
• .snx
• .sql
• .sr2
• .srf
• .srw
• .sum
• .svg
• .syncdb
• .t12
• .t13
• .tax
• .tor
• .txt
• .upk
• .vcf
• .vdf
• .vfs
• .vfs0
• .vpk
• .vpp_pc
• .vtf
• .w3x
• .wallet
• .wb2
• .wma
• .wmo
• .wmv
• .wotreplay
• .wpd
• .wps
• .x3f
• .xf
• .xlk
• .xls
• .xlsb
• .xlsm
• .xlsx
• .xxx
• .zip
• .ztm
• .ztmp

It opens the following files:

• %Desktop%\help_recover_instructions.HTM
• %Desktop%\help_recover_instructions.png
• %Desktop%\help_recover_instructions.TXT

(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.)

It deletes itself after execution.

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

• Infection status
• Bitcoin address
• Total size of encrypted files
• Malware version
• OS information
• Installation ID

NOTES:

It deletes shadow copies by executing the following command:

• vssadmin.exe delete shadows /all /Quiet

It changes boot configuration data (BCD) to disable the following:

• Emergency Management Services (EMS)
• Edit and advanced boot options at startup
• Windows startup repair and error recovery

It terminates processes containing the following strings:

• askmg
• rocex
• egedi
• sconfi
• cmd

It appends the extension .micro to the filename of the encrypted files.

It avoids encrypting files from the following directories:

• Windows
• Program Files
• %All Users Profile%\Application Data (Windows XP and below)
• ProgramData (Windows Vista and above)

It avoids encrypting files with the following strings:

• recove
• .micro

It drops HELP_RECOVER_instructions+{random 3 letters}.png, HELP_RECOVER_instructions+{random 3 letters}.txt, HELP_RECOVER_instructions+{random 3 letters}.html to the folders where the files are encrypted.

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