TROJ_CRYPTESLA.XXQP

May 27, 2015
 Analysis by: Cris Nowell Pantanilla
 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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.

  TECHNICAL DETAILS

File Size:

368,640 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

22 May 2015

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:

  • %AppDataLocal%\{Random Filename}.exe

(Note: %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local 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:

  • %AppDataLocal%\log.html - Contains the list of encrypted files.
  • %Desktop%\HELP_RESTORE_FILES.bmp
  • %Desktop%\HELP_RESTORE_FILES.txt
  • %Desktop%\Save_Files.lnk - Shortcut file pointing to the dropped copy
  • %AppDataLocal%\key.dat

(Note: %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local 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.)

It drops the following non-malicious files:

  • HELP_RESTORE_FILES_{random}.bmp
  • HELP_RESTORE_FILES_{random}.txt

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
mssvc = "%AppDataLocal%\{Random Filename}.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnce
mssvc = "%AppDataLocal%\{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_RESTORE_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:

  • ipinfo.io/ip

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

  • http://{BLOCKED}bzor5ybfto.tor2web.{BLOCKED}gie.de:443
  • http://{BLOCKED}bzor5ybfto.tor2web.org:443
  • http://{BLOCKED}8jhfali7fda.{BLOCKED}iewo492k.com/ping1.php
  • http://{BLOCKED}ncie82iaeow0.{BLOCKED}948sekod.com/ping1.php

It encrypts files with the following extensions:

  • sql
  • mp4
  • 7z
  • rar
  • m4a
  • wma
  • avi
  • wmv
  • csv
  • d3dbsp
  • zip
  • sie
  • sum
  • ibank
  • t13
  • t12
  • qdf
  • gdb
  • tax
  • pkpass
  • bc6
  • bc7
  • bkp
  • qic
  • bkf
  • sidn
  • sidd
  • mdd
  • ata
  • itl
  • itdb
  • icxs
  • hvpl
  • hplg
  • hkdbmdbackup
  • syncdb
  • gho
  • cas
  • svg
  • map
  • wmo
  • itm
  • sb
  • fos
  • mov
  • vdf
  • ztmp
  • sis
  • sid
  • ncf
  • menu
  • layout
  • dmp
  • blob
  • esm
  • vcf
  • vtf
  • dazip
  • fpk
  • mlx
  • kf
  • iwd
  • vpk
  • tor
  • psk
  • rim
  • w3x
  • fsh
  • ntl
  • arch00
  • lvl
  • snx
  • cfr
  • ff
  • vpp_pc
  • lrf
  • m2
  • mcmeta
  • vfs0
  • mpqge
  • kdb
  • db0
  • db
  • rofl
  • hkx
  • bar
  • upk
  • das
  • iwi
  • litemod
  • asset
  • forge
  • ltx
  • bsa
  • apk
  • re4
  • sav
  • lbf
  • slm
  • bik
  • epk
  • rgss3a
  • pak
  • big
  • unity3d
  • wotreplay
  • xxx
  • desc
  • py
  • m3u
  • flv
  • js
  • css
  • rb
  • png
  • jpeg
  • txt
  • p7c
  • p7b
  • p12
  • pfx
  • pem
  • crt
  • cer
  • der
  • x3f
  • srw
  • pef
  • ptx
  • r3d
  • rw2
  • rwl
  • raw
  • raf
  • orf
  • nrw
  • mrwref
  • mef
  • erf
  • kdc
  • dcr
  • cr2
  • crw
  • bay
  • sr2
  • srf
  • arw
  • 3fr
  • dng
  • jpe
  • jpg
  • cdr
  • indd
  • ai
  • eps
  • pdf
  • pdd
  • psd
  • dbf
  • mdf
  • wb2
  • rtf
  • wpd
  • dxg
  • xf
  • dwg
  • pst
  • accdb
  • mdb
  • pptm
  • pptx
  • ppt
  • xlk
  • xlsb
  • xlsm
  • xlsx
  • xls
  • wps
  • docm
  • docx
  • doc
  • odb
  • odc
  • odm
  • odp
  • ods
  • odt

It renames encrypted files using the following names:

  • {Original Filename}.exx

It deletes the initially executed copy of itself