Analysis by: Noel Anthony Llimos
ALIASES:

Trojan.Win32.Cosmu.doix (KASPERSKY), Ransom.Kovter (NORTON)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It encrypts files with specific file extensions.

  TECHNICAL DETAILS

File Size: 80,384 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 21 Sep 2017
Payload: Drops files, Modifies system registry, Terminates processes

Arrival Details

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

  • %AppDataLocal%\{Random Folder}\{Random Characters}.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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • Global\{GUID}
  • Local\{GUID}

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{Random Characters} = %AppDataLocal%\{Full Path of the Malware}\{Random Characters}.exe

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

  • %Start Menu%\Programs\Startup\{Random Characters}.lnk

(Note: %Start Menu% is the Start Menu folder, where it usually is C:\Documents and Settings\{user name}\Start Menu on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu 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.)

Other System Modifications

This Ransomware modifies the following registry entries:

HKEY_CURRENT_USER\Software\{Random}

Process Termination

This Ransomware terminates the following processes if found running in the affected system's memory:

  • sql
  • backup
  • restore
  • ocssd.exe
  • dbsnmp.exe
  • synctime.exe
  • mydesktopqos.exe
  • agntsvc.exeisqlpussvc.exe
  • xfssvccon.exe
  • mydesktopservice.exe
  • ocautoupds.exe
  • agntsvc.exeagntsvc.exe
  • firefoxconfig.exe
  • tbirdconfig.exe
  • ocomm.exe
  • dbeng50.exe
  • sqbcoreservice.exe
  • SDRSVC
  • SQLAgent
  • MSSQLBI
  • SQLWriter
  • MSSQL
  • SQLSERVERAGENT
  • MSSQLBI
  • MSSQLSERVER
  • MSQOLAP
  • MSQLBI
  • SQLBrowser
  • MsDtsServer100
  • ReportServer
  • MSSQLBI

Other Details

This Ransomware does the following:

  • It deletes shadow copies using the following commands:
    • /C vssadmin Delete Shadows /All /Quiet
    • /C wmic shadowcopy delete
    • /C Bcdedit.exe /set {default} recoveryenabled no
    • /C Bcdedit.exe /set {default} bootstatuspolicy ignoreallfailures

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • .docx
  • .pptx
  • .pptx
  • .xlsx
  • .xbap
  • .xps
  • .pdf
  • .pot
  • .hta
  • .xlt
  • .pps
  • .xlw.
  • .dot
  • .rtf
  • .ppt
  • .xls
  • .doc
  • .xml
  • .htm
  • .html
  • .hta
  • .exe
  • .search-ms
  • .mht
  • .zip
  • .dvr-ms
  • .wvx
  • .wmx
  • .wmv
  • .wm
  • .mpv2
  • .mpg
  • .mpeg
  • .mpe
  • .mpa
  • .mp2v
  • .mp2
  • .m1v
  • .IVF
  • .asx
  • .asf
  • .wax
  • .snd
  • .rmi
  • .m3u
  • .au
  • .aiff
  • .aifc
  • .aif
  • .midi
  • .mid
  • .wma
  • .wav
  • .mp3
  • .wmf
  • .tiff
  • .tif
  • .rle
  • .png
  • .jpeg
  • .jpe
  • .jpg
  • .jfif
  • .ico
  • .gif
  • .emf
  • .dib
  • .bmp

It avoids encrypting files with the following strings in their file name:

  • ntuser
  • normal.dot
  • containter.dat
  • UsrClass
  • WebCacheLock
  • WindowsUpdate
  • AUTOEXEC
  • boot
  • ntldr
  • .386
  • .73u
  • .8xu
  • .adm
  • .adml
  • .admx
  • .adv
  • .ani
  • .ann
  • .aos
  • .asec
  • .bat
  • .bcd
  • .bio
  • .bk2
  • .blf
  • .bmk
  • .bud
  • .cdmp
  • .chs
  • .ci
  • .clb
  • .cnt
  • .cpi
  • .cpl
  • .cpq
  • .com
  • .cur
  • .deslink
  • .deskthemepack
  • .dev
  • .diagcab
  • .diagcfg
  • .diagpkg
  • .dimax
  • .dit
  • .dlx
  • .dll
  • .dls
  • .dmp
  • .drv
  • .dss
  • .dvd
  • .dyc
  • .ebd
  • .efi
  • .exe
  • .ffa
  • .ffl
  • .ffo
  • .ffx
  • .ftg
  • .fts
  • .gmmp
  • .grl
  • .group
  • .grp
  • .h1s
  • .hdmp
  • .hhc
  • .hhk
  • .hiv
  • .hlp
  • .hpj
  • .hsh
  • .htt
  • .icl
  • .icns
  • .ico
  • .idi
  • .idx
  • .ime
  • .img3
  • .inf
  • .inf_loc
  • .ini
  • .ins
  • .ion
  • .itemdata-ms
  • .its
  • .jpn
  • .kbd
  • .kor
  • .library-ms
  • .lng
  • .lnk
  • .lib
  • .manifest
  • .mapimail
  • .mdmp
  • .mlc
  • .mnu
  • .msc
  • .msp
  • .msstyle
  • .msstyles
  • .mui
  • .mui_cccd5ae0
  • .mum
  • .mydocs
  • .nfo
  • .nls
  • .nt
  • .ntfs
  • .ocx
  • .p7b
  • .pck
  • .pdr
  • .pid
  • .pol
  • .ppd
  • .prf
  • .printerexport
  • .prt
  • .ps2
  • .pwl
  • .regtrans-ms
  • .rs
  • .rnd
  • .savedsearch
  • .scf
  • .scr
  • .sdb
  • .shd
  • .shsh
  • .str
  • .swp
  • .sys
  • .tha
  • .theme
  • .trx_dll
  • .uce
  • .vga
  • .vgd
  • .vx_
  • .vxd
  • .wdf
  • .wdgt
  • .webpnp
  • .wer
  • .wph
  • .wpx
  • .xrm-ms

It avoids encrypting files found in the following folders:

  • %System%
  • %Windows%
  • %internetcache%
  • %Temporary Internet Files%

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.. %Temporary Internet Files% is the Temporary Internet Files folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temporary Internet Files on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Microsoft\Windows\Temporary Internet Files on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), and Windows Server 2008; C:\Users\{user name}\AppData\Local\Microsoft\Windows\INetCache on Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), and Windows Server 2012.)

It appends the following extension to the file name of the encrypted files:

  • !-=solve a problem=-=grandums@gmail.com=-.PRIVAT66

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.672.04
FIRST VSAPI PATTERN DATE: 20 Sep 2017
VSAPI OPR PATTERN File: 13.673.00
VSAPI OPR PATTERN Date: 21 Sep 2017

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

Identify and terminate files detected as RANSOM_CRYPROTO.A

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

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_CURRENT_USER\Software
    • {Random}

Step 5

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 Characters} = %AppDataLocal%\{Random Folder}\{Random Characters}.exe

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.  
  • %AppDataLocal%\{Random Folder}\{Random Characters}.exe

Step 7

Scan your computer with your Trend Micro product to delete files detected as RANSOM_CRYPROTO.A. 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 the following Trend Micro Support pages for more information:

Step 8

Restore encrypted files from backup.

NOTES:

1. Enable services disabled using the command prompt.

2. Run cmd.exe as administrator.

3. To enable Windows Error Recovery Screen on Startup, use the following command: bcdedit /set {default} bootstatuspolicy displayallfailures

4. To enable Startup Repair, use the following command: /bcedit /set {default} recoveryenabled Yes


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