TROJ_CRYPCTB.YVN

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.

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:

• %User Temp%\{random characters 1}.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:

• %ProgramData%\{random characters 2}.html (contains ransom note and list of all encrypted files)
• %User Profile%\My Documents\!Decrypt-All-Files-{random characters 3}.txt (ransom note in text file)
• %User Profile%\My Documents\!Decrypt-All-Files-{random characters 3}.bmp (image used as wallpaper)
• {randomly selected path}\!Decrypt-All-Files-{random characters 3}.txt
• {randomly selected path}\!Decrypt-All-Files-{random characters 3}.bmp

(Note: %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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.. %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 drops the following files:

• %System%\Tasks\{random characters 4}.job

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
TileWallpaper = "0"

(Note: The default value data of the said registry entry is "User Preferences".)

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Profile%\My Documents\!Decrypt-All-Files-{random characters 3}.bmp"

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

NOTES:

This Trojan 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
• c
• cdr
• cer
• config
• cpp
• cr2
• crt
• crw
• cs
• dbf
• dbx
• dcr
• dd
• dds
• der
• dng
• doc
• docm
• docx
• dwg
• dxf
• dxg
• eps
• erf
• fdb
• gdb
• groups
• gsd
• gsf
• ims
• indd
• iss
• jpe
• jpeg
• 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
• pst
• ptx
• pwm
• py
• r3d
• raf
• rar
• raw
• rgx
• rik
• rtf
• rw2
• rwl
• safe
• sql
• srf
• srw
• txt
• vsd
• wb2
• wpd
• wps
• xlk
• xls
• xlsb
• xlsm
• xlsx
• zip