TROJ_CRYPCTB.P

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 may be dropped by other malware.

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It connects to certain websites to send and receive information.

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.

It may be dropped by the following malware:

• TROJ_DALEXIS.P

Installation

This Trojan drops the following copies of itself into the affected system and executes them:

• %User Temp%\{random file name}.exe

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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 drops the following files:

• %All Users Profile%\Application Data\{random characters}.html - contains ransom note and list of encrypted files
• %All Users Profile%\Application Data\{randomly selected folder }\{random file name} - private key
• %User Profile%\My Documents\!Decrypt-All_Files-{random letters}.bmp - wallpaper
• %User Profile%\My Documents\!Decrypt-All_Files-{random letters}.txt - ransom note in .txt file
• %System%\config\systemprofile\My Documents\!Decrypt-All_Files-{random letters}.bmp - wallpaper
• %System%\config\systemprofile\My Documents\!Decrypt-All_Files-{random letters}.txt - ransom note in .txt file
• %Windows%\Tasks\{random file name}.job - points to %User Temp%\{random file name}.exe

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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.. %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.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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 uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It injects codes into the following process(es):

• svchost.exe
• explorer.exe

Autostart Technique

The scheduled task executes the malware every:

• startup

Other System Modifications

This Trojan changes the desktop wallpaper by modifying the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
TileWallpaper = "0"

(Note: The default value data of the said registry entry is {user-defined}.)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Profile%\My Documents\!Decrypt-All_Files-{random letters}.bmp"

(Note: The default value data of the said registry entry is {user-defined}.)

Other Details

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

• {BLOCKED}m4qk625n6.tor2web.{BLOCKED}gie.de
• {BLOCKED}m4qk625n6.tor2web.org
• {BLOCKED}m4qk625n6.tor2web.fi
• {BLOCKED}m4qk625n6.onion.cab
• {BLOCKED}m4qk625n6.onion.lt
• {BLOCKED}m4qk625n6.onion.gq
• {BLOCKED}4qk625n6.tor2web.{BLOCKED}gie.de
• {BLOCKED}4qk625n6.tor2web.fi
• {BLOCKED}3cad3kn7v.onion
• {BLOCKED}3cad3kn7v.onion.cab
• {BLOCKED}3cad3kn7v.tor2web.org
• {BLOCKED}k625n6.tor2web.fi

It encrypts files with the following extensions:

• 3fr
• 7z
• abu
• accdb
• ai
• arp
• arw
• bas
• bay
• bdcr
• bdcu
• bdd
• bdp
• bds
• blend
• bpdr
• bpdu
• bsdr
• bsdu
• cdr
• cer
• config
• cpp
• cr2
• crt
• crw
• cs
• dbf
• dbx
• dcr
• dds
• dd
• der
• dng
• docm
• doc
• docx
• dwg
• dxf
• dxg
• eps
• erf
• fdb
• gdb
• groups
• gsd
• gsf
• ims
• indd
• iss
• jpeg
• jpe
• jpg
• js
• kdc
• kwm
• md
• mdb
• mdf
• mef
• mrw
• nef
• nrw
• odb
• odm
• odp
• ods
• odt
• orf
• p12
• p7b
• p7c
• pas
• pdd
• pdf
• pef
• pem
• pfx
• php
• pl
• ppt
• pptm
• pptx
• psd
• pst
• ptx
• pwm
• py
• r3d
• raf
• rar
• raw
• rgx
• rik
• rtf
• rw2
• rwl
• safe
• sql
• srf
• srw
• txt
• vsd
• wb2
• wpd
• wps
• xlk
• xls
• xlsm
• xlsx
• xlsb
• zip

It renames encrypted files using the following names:

• {original file name}.{random letters}

NOTES:

The dropped file Decrypt-All-Files-{random characters}.txt contains the following ransom message:

This Trojan sets the system's desktop wallpaper to the following image:

It displays the ransom message in seven different languages: French, Spanish, Latvian, German, Dutch, Italian and English

It can decrypt five random files to entice the user that it is capable of recovering the files after payment of ransom:

If the connection to the server is established, it saves the details of the private key in %All Users Profile%\Application Data\{randomly selected folder }\{random file name}.

It then asks the user to pay the ransom in bitcoin to automatically decrypt the files. It also contain instructions how to buy bitcoins via cash, electronic currency and etc. If the connection is not established, it provides instructions to the user how to pay the ransom in another computer with internet connection.

This Trojan deletes all Windows Shadow Copies found in the system. It deletes copies of itself and its scheduled task after the time expires.