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RANSOM_CRYPSHED.F

October 12, 2015
 Analysis by: Janus Agcaoili
 ALIASES:

Troj/Ransom-AWQ (Sophos), Trojan:Win32/Bagsu!rfn (Microsoft), Trojan-Ransom.Win32.Shade.ub (Kaspersky),

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


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 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:

897,024 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

15 Sep 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.

Installation

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

  • For Windows XP and below:
    • %All Users Profile%\Application Data\Windows\csrss.exe
  • For Windows Vista and above:
    • %All Users Profile%\Windows\csrss.exe
    • %System Root%\Users\All Users\Windows\csrss.exe

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

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\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%\Windows\csrss.exe" (For Windows Vista and above)

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

It drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\system.pif
    (Note: %User Startup% is usually C:\Users\{User Name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup for Windows 7)

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\System32\
Configuration

It modifies the following registry keys:

HKEY_USERS\{SID}\Control Panel\
Desktop
Wallpaper = "%Application Data%\{8 Random clphanumeric characters}{Same characters as first 8}.bmp"

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

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%Application Data%\{8 Random alphanumeric characters}{Same characters as first 8}.bmp"

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

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
  • As of this writing, the downloaded file can be any of the following:
    • TSPY_FAREIT.BTSHD
    • TROJ_MIUREF.BTSHD
    • WORM_KELIHOS.BTSHD
    • TROJ_BRUTESHED.A

(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:

  • http://myip.ru

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

  • {BLOCKED}.{BLOCKED}.21.38
  • {BLOCKED}.{BLOCKED}.238.52
  • {BLOCKED}.{BLOCKED}.193.9
  • {BLOCKED}.{BLOCKED}.244.244
  • {BLOCKED}.{BLOCKED}.0.34
  • {BLOCKED}.{BLOCKED}.206.212
  • {BLOCKED}.{BLOCKED}.40.189
  • {BLOCKED}.{BLOCKED}.175.225
  • http://{BLOCKED}5s4fss2q.onion/reg.php
  • http://{BLOCKED}55s4fss2q.onion/err.php
  • http://{BLOCKED}55s4fss2q.onion/prog.php
  • http://{BLOCKED}55s4fss2q.onion/cmd.php
  • http://{BLOCKED}55s4fss2q.onion/sys.php

It encrypts files with the following extensions:

  • wb2
  • cdr
  • srw
  • p7b
  • odm
  • mdf
  • p7c
  • 3fr
  • der
  • odb
  • arw
  • rwl
  • cer
  • xlk
  • pdd
  • rw2
  • crt
  • dx
  • r3d
  • pem
  • bay
  • ptx
  • pfx
  • indd
  • nrw
  • p12
  • bd
  • backup
  • torrent
  • kwm
  • pwm
  • safe
  • xl
  • xls
  • xlsx
  • xlsm
  • xlsb
  • xltm
  • xlt
  • xlam
  • xla
  • mdb
  • rtf
  • txt
  • xml
  • csv
  • pdf
  • prn
  • dif
  • slk
  • ods
  • xltx
  • xlm
  • odc
  • xlw
  • uxdc
  • pm
  • udl
  • dsn
  • iqy
  • dqy
  • rqy
  • oqy
  • cub
  • bak
  • xsn
  • xsf
  • xtp
  • xtp2
  • accdb
  • adb
  • adp
  • mda
  • accda
  • mde
  • accde
  • accdw
  • accdt
  • accdc
  • mdw
  • dbf
  • tab
  • asc
  • frm
  • opt
  • myd
  • myi
  • db
  • onetoc2
  • one
  • onepkg
  • vcs
  • ics
  • pst
  • oft
  • msg
  • pptx
  • ppt
  • pptm
  • pps
  • ppsm
  • pot
  • potx
  • potm
  • odp
  • thmx
  • wpd
  • wps
  • ppa
  • ppam
  • wmf
  • emf
  • pub
  • ps
  • xps
  • vsd
  • vdx
  • vss
  • vsx
  • vst
  • vtx
  • vsw
  • vdw
  • emz
  • dwg
  • dxf
  • docx
  • doc
  • docm
  • dotx
  • dot
  • dotm
  • djvu
  • chm
  • htm
  • html
  • mht
  • mhtml
  • shtml
  • shtm
  • asp
  • aspx
  • dwt
  • stm
  • cs
  • css
  • psd
  • pdd
  • 3ds
  • max
  • crw
  • nef
  • raf
  • orf
  • mrw
  • dcr
  • mos
  • pef
  • srf
  • dng
  • x3f
  • cr2
  • erf
  • sr2
  • kdc
  • mfw
  • mef
  • cin
  • sdpx
  • dpx
  • fido
  • dae
  • dcm
  • dc3
  • dic
  • eps
  • kmz
  • iff
  • tdi
  • exr
  • pcx
  • pdp
  • pxr
  • sct
  • u3d
  • obj
  • ai3
  • ai4
  • ai5
  • ai6
  • ai7
  • ai8
  • ai
  • epsp
  • epsf
  • hdr
  • rgbe
  • xyze
  • flm
  • pbm
  • pgm
  • ppm
  • pnm
  • pfm
  • pam
  • pct
  • pict
  • psb
  • fxg
  • swf
  • hta
  • htc
  • ssi
  • as
  • asr
  • xsl
  • xsd
  • dtd
  • xslt
  • rss
  • rdf
  • lbi
  • asa
  • ascx
  • asmx
  • config
  • cfm
  • cfml
  • cfc
  • tld
  • phtml
  • jsp
  • wml
  • tpl
  • lasso
  • jsf
  • vb
  • vbs
  • vtm
  • vtml
  • 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
  • 1cd
  • dt
  • cf
  • cfu
  • mxl
  • epf
  • vrp
  • grs
  • geo
  • elf
  • lgf
  • lgp
  • log
  • st
  • pff
  • mft
  • efd
  • md
  • xsn

It renames encrypted files using the following names:

  • "{Encrypted String}.xtbl"
  • "{Original File Name}.ytbl" - if file name encryption fails

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.926.06

FIRST VSAPI PATTERN DATE:

18 Sep 2015

VSAPI OPR PATTERN File:

11.927.00

VSAPI OPR PATTERN Date:

19 Sep 2015

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

Restart in Safe Mode

[ Learn More ]

Step 4

Delete this registry value

[ 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.


  • For Windows XP and below:
    In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Client Server Runtime Subsystem = "%All Users Profile%\Application Data\Windows\csrss.exe"
  • For Windows Vista and above:
    In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Client Server Runtime Subsystem = "%All Users Profile%\Windows\csrss.exe"

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\System32
    • Configuration

Step 6

Restore this modified registry value

[ 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_USERS\{SID}\Control Panel\Desktop
    • From: Wallpaper = "%Application Data%\{8 Random clphanumeric characters}{Same characters as first 8}.bmp"
      To: Wallpaper = "{user-defined wallpaper}"
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: Wallpaper = "%Application Data%\{8 Random alphanumeric characters}{Same characters as first 8}.bmp"
      To: Wallpaper = "{user-defined wallpaper}"

Step 7

Search and delete this file

[ 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.
  • %User Temp%\cached-certs
  • %User Temp%\cached-microdesc-consensus
  • %User Temp%\cached-microdescs.new
  • %User Temp%\lock
  • %User Temp%\state
  • %Application Data%\{8 Random Alphanumeric Characters}{Same Characters as first 8}.bmp
  • {Root Drives}\README{number 1 to 10}.txt
  • %System Root%\Users\Public\Desktop\README{number 1 to 10}.txt (For 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

Step 8

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

    • TSPY_FAREIT.BTSHD
    • TROJ_MIUREF.BTSHD
    • WORM_KELIHOS.BTSHD
    • TROJ_BRUTESHED.A

Step 9

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • {Files with affected extensions}

Step 10

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_CRYPSHED.F. 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.

Step 11

Restoring the Screen Saver

  1. Open the Display window. To do this:
    • On Windows 2000, XP, and Server 2003:
      Click Start>Settings>Control Panel, double-click on Display, and choose the Screen Saver tab.
    • On Windows Vista, 7, Server 2008 and Server 2008:
      Click Start>Control Panel>Appearance and Personalization>Change screen saver.
    • On Windows 8, 8.1, and Server 2012:
      Right-click on the lower left corner of the screen, click Control Panel>Appearance and Personalization>Change screen saver.
  2. Click on Settings. Delete the string on the text field, then click OK.
  3. Select any screen saver to replace the existing.
  4. Click Apply. Close the window.


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