Analysis by: Anthony Joe Melgarejo
ALIASES:

Ransom:Win32/Crowti (Microsoft), Ransom-CWall.b (McAfee), Trojan.Cryptodefense (Symantec), Trojan-Ransom.Win32.Cryptodef.aaoj (Kaspersky),

 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

Infection Channel: Downloaded from the Internet, Spammed via email

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It may be dropped by other malware.

It connects to certain websites to send and receive information. It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 331,776 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 02 Nov 2015
Payload: Connects to URLs/IPs, Encrypts files

Arrival Details

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It may be dropped by other malware.

Installation

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

  • %Application Data%\{random 8 characters}\{random 10 characters}.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:

    It drops and executes the following files:

    • %Desktop%\HELP_YOUR_FILES.HTML
    • %Desktop%\HELP_YOUR_FILES.PNG
    • %Desktop%\HELP_YOUR_FILES.TXT

    (Note: %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 adds the following processes:

    • explorer.exe
    • svchost.exe

    It is injected into the following processes running in memory:

    • created explorer.exe
    • created svchost.exe

    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
    {random 8 characters} = "%Application Data%\{random 8 characters}\{random 10 characters}.exe"

    Other System Modifications

    This Trojan modifies the following registry entries:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
    Windows NT\CurrentVersion\SystemRestore
    DisableSR = "1"

    (Note: The default value data of the said registry entry is 0.)

    Other Details

    This Trojan connects to the following website to send and receive information:

    • http://{BLOCKED}dia.com/1LaXd8.php
    • http://{BLOCKED}owacademy.com/5_YQDI.php
    • http://{BLOCKED}juice.com/z9r0qh.php
    • http://{BLOCKED}od.com/HS0ILJ.php
    • http://{BLOCKED}australia.com/8gX7hN.php
    • http://{BLOCKED}fter60.com/iCqjno.php
    • http://{BLOCKED}acts.com/EiFSId.php
    • http://{BLOCKED}tt.com/YuF59b.php
    • http://{BLOCKED}ational.com/eRs70a.php
    • http://{BLOCKED}ep.com/OIsSCj.php
    • http://{BLOCKED}ter60.com/r_kfhH.php
    • http://{BLOCKED}china.com/etdhIk.php
    • http://{BLOCKED}07.com/VoZQ_j.php
    • http://{BLOCKED}leinc.com/yL54uH.php
    • http://{BLOCKED}udoula.com/GH09Dp.php
    • http://{BLOCKED}ong.com/yzoLR7.php
    • http://{BLOCKED}op.lk/6872VF.php
    • http://{BLOCKED}aj.com/60wEBT.php
    • http://{BLOCKED}er.com/uVRfPv.php
    • http://{BLOCKED}les.in/ZUQce4.php
    • http://{BLOCKED}igns.com/E8B2gt.php
    • http://{BLOCKED}hare.org/WEAbCT.php
    • http://{BLOCKED}hu.in/zJE0fD.php
    • http://{BLOCKED}ting.net/XEGeuI.php
    • http://{BLOCKED}r.com/dA91lI.php
    • http://{BLOCKED}einfo.com/zDJRc8.php
    • http://{BLOCKED}ional.com/AYNILr.php

    It encrypts files with the following extensions:

    • 3fr
    • 3dm
    • 3ds
    • 3gp
    • 3g2
    • 3pr
    • 7z
    • +MuhD
    • ab4
    • accdb
    • accde
    • accdp
    • accdr
    • accdt
    • accdu
    • ach
    • acr
    • act
    • adb
    • ads
    • agdl
    • ait
    • ai
    • al
    • apj
    • arw
    • asf
    • asm
    • asp
    • asx
    • avi
    • awg
    • back
    • backup
    • backupdb
    • bak
    • bank
    • bay
    • bdb
    • bgt
    • bik
    • bkf
    • bkp
    • blend
    • bpw
    • cdb
    • cdf
    • cdr
    • cdr6
    • cdrw
    • cdr5
    • cdr3
    • cdr4
    • cdx
    • ce1
    • ce2
    • cer
    • cfp
    • cgm
    • c
    • cib
    • class
    • cls
    • cmt
    • cnv
    • cpi
    • cpp
    • cr2
    • craw
    • crt
    • crw
    • csh
    • csl
    • csv
    • cs
    • dac
    • db-journal
    • db3
    • db
    • dbf
    • dbr
    • dbs
    • dc2
    • dcr
    • dcs
    • dcx
    • ddd
    • ddoc
    • ddrw
    • dds
    • der
    • des
    • design
    • dgc
    • djvu
    • dng
    • doc
    • docm
    • docx
    • dot
    • dotm
    • dotx
    • drf
    • drw
    • dtd
    • dwg
    • dxb
    • dxf
    • dxg
    • ebd
    • edb
    • eml
    • eps
    • erbsql
    • erf
    • exf
    • fdb
    • ffd
    • fff
    • fhd
    • fh
    • fla
    • flac
    • flv
    • fm
    • fp7
    • fpx
    • fxg
    • gdb
    • gray
    • grey
    • grw
    • gry
    • hbk
    • hpp
    • h
    • ibank
    • ibd
    • ib
    • ibz
    • idx
    • iif
    • iiq
    • incpas
    • indd
    • itdb
    • java
    • jpe
    • jpeg
    • jpg
    • kc2
    • kdbx
    • kdc
    • key
    • kpdx
    • lua
    • m4v
    • maf
    • mam
    • maq
    • mar
    • maw
    • max
    • mdb
    • mdc
    • mde
    • mdf
    • mdt
    • mef
    • mfw
    • mmw
    • moneywell
    • m
    • mos
    • mov
    • mp3
    • mp4
    • mpg
    • mpp
    • mrw
    • mso
    • myd
    • ndd
    • nd
    • nef
    • nk2
    • nop
    • nrw
    • ns2
    • ns3
    • ns4
    • nsd
    • nsf
    • nsg
    • nsh
    • nwb
    • nx1
    • nx2
    • nxl
    • nyf
    • obj
    • odb
    • odc
    • odf
    • odg
    • odm
    • odp
    • ods
    • odt
    • oil
    • one
    • orf
    • otg
    • oth
    • otp
    • ots
    • ott
    • p12
    • p7b
    • p7c
    • pages
    • pas
    • pat
    • pbo
    • pcd
    • pct
    • pdb
    • pdd
    • pdf
    • pef
    • pem
    • pfx
    • php
    • pip
    • plc
    • pl
    • pot
    • potm
    • potx
    • ppam
    • pps
    • ppsx
    • ppsm
    • ppt
    • pptm
    • pptx
    • prf
    • ps
    • psafe3
    • psd
    • pspimage
    • ptx
    • pub
    • puz
    • py
    • qba
    • qbb
    • qbm
    • qbr
    • qbw
    • qbx
    • qby
    • r3d
    • raf
    • rar
    • rat
    • raw
    • rdb
    • rm
    • rpmsg
    • rtf
    • rw2
    • rwl
    • rwz
    • s3db
    • sas7bdat
    • say
    • sd0
    • sda
    • sdf
    • sl2
    • sldm
    • sldx
    • snp
    • sqlite3
    • sql
    • sqlite
    • sqlitedb
    • sr2
    • srf
    • srt
    • srw
    • st4
    • st5
    • st6
    • st7
    • st8
    • std
    • sti
    • stw
    • stx
    • svg
    • swf
    • sxc
    • sxd
    • sxg
    • sxi
    • sxm
    • sxw
    • tex
    • tga
    • thm
    • tlg
    • txt
    • vob
    • vsx
    • vtx
    • wallet
    • wav
    • wb2
    • wll
    • wmv
    • wpd
    • wps
    • x11
    • x3f
    • xis
    • xla
    • xlam
    • xlb
    • xlc
    • xlk
    • xll
    • xlm
    • xlr
    • xls
    • xlsx
    • xlsm
    • xlsb
    • xlt
    • xltx
    • xltm
    • xlw
    • xpp
    • xsn
    • ycbcra
    • yuv
    • zip

    It deletes the initially executed copy of itself

    NOTES:

    It searches all drives for files to encrypt except CD_ROM drive.

    It deletes shadow copies by executing the following command:

    • vssadmin.exe Delete Shadows /All /Quiet

    It avoids encrypting files with the following extensions:

    • application
    • bat
    • cmd
    • com
    • cpl
    • dll
    • exe
    • gadget
    • hta
    • msc
    • msi
    • msp
    • pif
    • scf
    • scr
    • sys

    It avoids encrypting files with the following file name:
    • p0r4dime.1!
    • thumbs.db

    It avoids encrypting files within the following folder names:
    • "."
    • Temp
    • Y@Cs
    • cache
    • cache2
    • games
    • nvidia
    • packages
    • uvOyR
    • windows

    It renames encrypted files using the following names:

    • {5 to 10 alphanumeric characters}.{2 to 5 alphanumeric characters}

    It encrypts the file names of the encrypted files.

    It displays the following ransom notes:











    Once the victim access the payment site specified in the ransom note, the browser will be display the following "Decrypt Service" site:

      SOLUTION

    Minimum Scan Engine: 9.750
    FIRST VSAPI PATTERN FILE: 12.126.07
    FIRST VSAPI PATTERN DATE: 02 Nov 2015
    VSAPI OPR PATTERN File: 12.127.00
    VSAPI OPR PATTERN Date: 02 Nov 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.

    • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
      • {random 8 characters} = "%Application Data%\{random 8 characters}\{random 10 characters}.exe"

    Step 5

    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.

    • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRestore
      • From: DisableSR = "1"
        To: DisableSR = 0

    Step 6

    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.
    • HELP_YOUR_FILES.HTML
    • HELP_YOUR_FILES.PNG
    • HELP_YOUR_FILES.TXT

    Step 7

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


    Did this description help? Tell us how we did.