Analysis by: Mar Philip Elaurza
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet

This Trojan may be downloaded by other malware/grayware from remote sites.

It downloads a file from a certain URL then renames it before storing it in the affected system. It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

It connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size: 952,832 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 06 Apr 2016
Payload: Connects to URLs/IPs, Downloads files, Encrypts files, Steals information

Arrival Details

This Trojan may be downloaded by the following malware/grayware from remote sites:

  • JS_CRYPSHED.B

Installation

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

  • %All Users Profile%\Application Data\Windows\csrss.exe (Windows XP and below)
  • %All Users Profile%\Windows\csrss.exe (Windows Vista and above)

(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.)

It drops the following files:

  • %Application Data%\{8 Random Alphanumeric Characters}{Same Characters as first 8}.bmp
  • %User Temp%\cached-certs
  • %User Temp%\cached-microdesc-consensus
  • %User Temp%\cached-microdescs.new
  • %User Temp%\lock
  • %User Temp%\state

(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.. %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 leaves text files that serve as ransom notes containing the following:

  • {Root Drives}\README{number 1 to 10}.txt
  • %System Root%\Users\Public\Public Desktop\README{number 1 to 10}.txt (Windows Vista and Above)
  • %All Users Profile%\Desktop\README{number 1 to 10}.txt (For Windows XP and Below)
  • %Desktop%\README{number 1 to 10).txt

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Client Server Runtime Subsystem = %All Users Profile%\Application Data\Windows\csrss.exe (Windows XP and below)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Client Server Runtime Subsystem = %All Users Profile%\Windows\csrss.exe (Windows Vista and above)

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\System32\
Configuration

HKEY_CURRENT_USER\SOFTWARE\System32\
Configuration

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\System32\
Configuration
pk = {PUBLIC KEY}

HKEY_LOCAL_MACHINE\SOFTWARE\System32\
Configuration
cnt = {numbers}

HKEY_LOCAL_MACHINE\SOFTWARE\System32\
Configuration
mode = 0

HKEY_LOCAL_MACHINE\SOFTWARE\System32\
Configuration
state = 5

HKEY_LOCAL_MACHINE\SOFTWARE\System32\
Configuration
i = {random characters}

HKEY_LOCAL_MACHINE\SOFTWARE\System32\
Configuration
Version = 7.2.0.3

HKEY_CURRENT_USER\SOFTWARE\System32\
Configuration
pk = {PUBLIC KEY}

HKEY_CURRENT_USER\SOFTWARE\System32\
Configuration
cnt = {numbers}

HKEY_CURRENT_USER\SOFTWARE\System32\
Configuration
mode = 0

HKEY_CURRENT_USER\SOFTWARE\System32\
Configuration
state = 3

HKEY_CURRENT_USER\SOFTWARE\System32\
Configuration
i = {random characters}

HKEY_CURRENT_USER\SOFTWARE\System32\
Configuration
Version = 7.2.0.3

HKEY_LOCAL_MACHINE\SOFTWARE\System32\
Configuration
sys = 1

HKEY_CURRENT_USER\SOFTWARE\System32\
Configuration
sys = 1

It modifies the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
wp = "%Application Data%\{random characters}.bmp"

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

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

  • %Application Data%\{8 random alphanumeric characters}{Same characters as first 8}.bmp

Download Routine

This Trojan downloads files from the following URLs then renames them before storage in the affected system:

  • URLs varies based from the list received from the servers

It saves the files it downloads using the following names:

  • %User Temp%\{8 Random Alphanumeric Strings}.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 then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

Information Theft

This Trojan gathers the following data:

  • Computer Information
  • Network Information
  • IP Address
  • List of Logical Drives
  • User Name
  • OS Version

Other Details

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

  • whatismyipaddress.com

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

  • http://{server}/{path}

    where {server} can be any of the following:
    • {BLOCKED}.{BLOCKED}.40.189
    • {BLOCKED}.{BLOCKED}.32.5
    • {BLOCKED}.{BLOCKED}.0.39
    • {BLOCKED}.{BLOCKED}.21.38
    • {BLOCKED}.{BLOCKED}.206.212
    • {BLOCKED}.{BLOCKED}.251.203
    • {BLOCKED}.{BLOCKED}.17.194
    • {BLOCKED}.{BLOCKED}.244.244
    • {BLOCKED}.{BLOCKED}.223.34
    • {BLOCKED}.{BLOCKED}.193.9
    • http://{BLOCKED}h2ldj3v.onion
    and where {path} can be any of the following:
    • reg.php
    • prog.php
    • err.php
    • cmd.php
    • sys.php


It encrypts files with the following extensions:

  • edml
  • raw
  • jpg
  • jpeg
  • jpe
  • bmp
  • png
  • tif
  • tiff
  • dib
  • gif
  • svg
  • svgz
  • rle
  • tga
  • vda
  • icb
  • wbm
  • wbmp
  • jpf
  • jpx
  • jp2
  • j2k
  • j2c
  • jpc
  • avi
  • mkv
  • mov
  • mp4
  • wmv
  • 3gp
  • mpg
  • mpeg
  • m4v
  • divx
  • mpv
  • m1v
  • dat
  • anim
  • m4a
  • qt
  • 3g2
  • f4v
  • mkidx
  • mka
  • avs
  • vdr
  • flv
  • bin
  • mp3
  • wav
  • asx
  • pls
  • zip
  • 7z
  • rar
  • tar
  • gz
  • bz2
  • wim
  • xz
  • c
  • h
  • hpp
  • cpp
  • php
  • php3
  • php4
  • php5
  • py
  • pl
  • sln
  • js
  • json
  • inc
  • sql
  • java
  • class
  • ini
  • asm
  • clx
  • tbb
  • tbi
  • tbk
  • pst
  • dbx
  • cbf
  • crypted
  • tib
  • eml
  • fld
  • vbm
  • vbk
  • vib
  • vhd
  • 1cd
  • dt
  • cf
  • cfu
  • mxl
  • epf
  • vrp
  • grs
  • geo
  • elf
  • lgf
  • lgp
  • log
  • st
  • pff
  • mft
  • efd
  • md
  • dmp
  • fdb
  • lst
  • fbk
  • sw
  • vdw

It renames encrypted files using the following names:

  • {random characters}.better_call_saul
  • {Original File Name}.los_pollos - if filename encryption fails

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.450.06
FIRST VSAPI PATTERN DATE: 06 Apr 2016
VSAPI OPR PATTERN File: 12.451.00
VSAPI OPR PATTERN Date: 07 Apr 2016

Step 1

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

Step 2

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 3

Remove the malware/grayware file that dropped/downloaded RANSOM_CRYPSHED.D. (Note: Please skip this step if the threat(s) listed below have already been removed.)