TROJ_CRYPTESLA.A

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.

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 Filename}.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 drops the following files:

• %Application Data%\log.html - Contains the list of encrpted files.
• %Desktop%\HELP_TO_SAVE_FILES.bmp
• %Desktop%\HELP_TO_SAVE_FILES.txt
• %Desktop%\Save_Files.lnk - Shortcut file pointing to the dropped copy
• %Application Data%\key.dat

(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.. %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.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
wertret = "%Application Data%\{Random Filename}.exe"

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
wertret = "%Application Data%\{Random Filename}.exe"

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
WallpaperStyle = "0"

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

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 = "%Desktop%\HELP_TO_SAVE_FILES.bmp"

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

Process Termination

This Trojan terminates processes or services that contain any of the following strings if found running in the affected system's memory:

• taskmgr
• procexp
• regedit
• msconfig
• cmd.exe

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Other Details

This Trojan connects to the following URL(s) to get the affected system's IP address:

• http://{BLOCKED}o.io/ip

It connects to the following website to send and receive information:

• http://{BLOCKED}ftmf7lelsa.{BLOCKED}7awmx28.com
• http://{BLOCKED}ftmf7lelsa.{BLOCKED}4iene29.com
• http://{BLOCKED}ftmf7lelsa.{BLOCKOED}b.blutmagie.de:443
• http://{BLOCKED}ftmf7lelsa.{BLOCKED}b.fi:443

It encrypts files with the following extensions:

• .3fr
• .DayZProfile
• .accdb
• .ai
• .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
• .dbfv
• .dcr
• .der
• .desc
• .dmp
• .dng
• .doc
• .docm
• .docx
• .dwg
• .dxg
• .ecc
• .epk
• .eps
• .erf
• .esm
• .ff
• .flv
• .forge
• .fos
• .fpk
• .fsh
• .gdb
• .gho
• .hkdb
• .hkx
• .hplg
• .hvpl
• .ibank
• .icxs
• .indd
• .itdb
• .itl
• .itm
• .iwd
• .iwi
• .jpe
• .jpeg
• .jpg
• .js
• .kdb
• .kdc
• .kf
• .layout
• .lbf
• .litemod
• .lrf
• .ltx
• .lvl
• .m2
• .m3u
• .m4a
• .map
• .mcgame
• .mcmeta
• .mdb
• .mdbackup
• .mddata
• .mdf
• .mef
• .menu
• .mlx
• .mpqge
• .mrwref
• .ncf
• .nrw
• .ntl
• .odb
• .odc
• .odm
• .odp
• .ods
• .odt
• .orf
• .p12
• .p7b
• .p7c
• .pak
• .pdd
• .pdf
• .pef
• .pem
• .pfx
• .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
• .sc2save
• .sid
• .sidd
• .sidn
• .sie
• .sis
• .slm
• .snx
• .sr2
• .srf
• .srw
• .sum
• .svg
• .syncdb
• .t12
• .t13
• .tax
• .tor
• .txt
• .unity3d
• .upk
• .vcf
• .vdf
• .vfs0
• .vpk
• .vpp_pc
• .vtf
• .w3x
• .wb2
• .wma
• .wmo
• .wmv
• .wotreplay
• .wpd
• .wps
• .x3f
• .xf
• .xlk
• .xls
• .xlsb
• .xlsm
• .xlsx
• .xxx
• .ztmp

It deletes the initially executed copy of itself

NOTES:

It creates and displays the following window to inform the user about what happened to their files and how they can restore them.

The registry modifications are for changing the affected system's wallpaper. The new wallpaper informs the user that his files are encrypted and displays the instructions on how to decrypt the files.