Analysis by: Joachim Suico

ALIASES:

Win32:Crypt-RXH [Trj] (Avast); Win32/Filecoder.EM (ESET-NOD32); Trojan.Agent.ED (Malwarebytes)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: Yes

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

This crypto-ransomware is one of the malware payloads of Fiesta exploit kit. Typically, exploit kits are used to deliver or spread threats.

To get a one-glance comprehensive view of the behavior of this Trojan, refer to the Threat Diagram shown below.

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 connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size: 332,313 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 18 Mar 2015
Payload: Encrypts files, Connects to URLs/IPs

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 other malware.

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 current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It drops the following files:

  • %Application Data%\key.dat
  • %Application Data%\log.html (list of all encrypted files)
  • %Desktop%\HELP_RESTORE_FILES.bmp
  • %Desktop%\HELP_RESTORE_FILES.txt
  • %Desktop%\CryptoLocker.lnk (shortcut for dropped copy)

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • System1230123

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
svv_e = "%Application Data%\{random filename}.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnce
*svv_e = "%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_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:

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

Other Details

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

  • http://ipinfo.io/ip

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

  • https://{BLOCKED}ib47vlep5o.tor2web.fi
  • https://{BLOCKED}ib47vlep5o.tor2web.blutmagie.de
  • https://{BLOCKED}ib47vlep5o.42kjb11.net
  • https://{BLOCKED}q26q2h4jkzj.2kjb10.net

NOTES:

It encrypts files with the following extensions in all folders found in the physical drives and appends .ECC as the new file extension of the encrypted files:

  • .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
  • .mddata
  • .itl
  • .itdb
  • .icxs
  • .hvpl
  • .hplg
  • .hkdb
  • .mdbackup
  • .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
  • .jp
  • .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 deletes shadow copies by executing the following command:

  • %System%\vssadmin.exe delete shadows /all /Quiet

It sets the system's desktop wallpaper to the following image:

It demands payment for using decryption service:

  SOLUTION

Minimum Scan Engine: 9.750
FIRST VSAPI PATTERN FILE: 11.561.00
FIRST VSAPI PATTERN DATE: 26 Mar 2015
VSAPI OPR PATTERN File: 11.561.00
VSAPI OPR PATTERN Date: 26 Mar 2015

Step 1

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 2

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 3

Scan your computer with your Trend Micro product and note files detected as TROJ_CRYPTESLA.CAG

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

Delete this registry key

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • svv_e = "%Application Data%\{random filename}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce
    • *svv_e = "%Application Data%\{random filename}.exe"

Step 6

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • From: WallpaperStyle = "0"
  • To: WallpaperStyle = "{User Preferences}"
  • From: TileWallpaper = "0"
  • To: TileWallpaper = "{User Preferences}"
  • From: Wallpaper = "%Desktop%\HELP_TO_SAVE_YOUR_FILES.bmp"
  • To: Wallpaper = "{User Preferences}"

Step 7

Search and delete these files

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %Application Data%\key.dat
  • %Application Data%\log.html
  • %Desktop%\HELP_RESTORE_FILES.bmp
  • %Desktop%\HELP_RESTORE_FILES.txt
  • %Desktop%\CryptoLocker.lnk

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_CRYPTESLA.CAG. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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