Analysis by: Mohammed Malubay

ALIASES:

Win64/Filecoder.Netwalker.A trojan (NOD32);

 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, Downloaded from the Internet

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 drops files as ransom note. It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size: 5,348,403 bytes
File Type: PS1
Memory Resident: No
Initial Samples Received Date: 06 May 2020
Payload: Disables services, Terminates processes, Displays message/message boxes, Encrypts files

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 files:

  • %User Temp%\{random characters}-.tmp
  • %User Temp%\{random characters}-.0.cs
  • %User Temp%\{random characters}-.dll
  • %User Temp%\{random characters}-.cmdline
  • %User Temp%\{random characters}-.out
  • %User Temp%\{random characters}-.err
  • %User Temp%\{random characters}-.pdb
  • %User Temp%\{random characters}.tmp
  • %User Temp%\{random characters}.0.cs
  • %User Temp%\{random characters}.dll
  • %User Temp%\{random characters}.cmdline
  • %User Temp%\{random characters}.out
  • %User Temp%\{random characters}.err
  • %User Temp%\{random characters}.pdb

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

It adds the following processes:

  • %Windows%\Microsoft.NET\Framework\{version}\csc.exe /noconfig /fullpaths @"%User Temp%\{random characters}-.cmdline"
  • %Windows%\Microsoft.NET\Framework\{version}\cvtres.exe /NOLOGO /READONLY /MACHINE:IX86 "/OUT:%User Temp%\{random characters}.tmp"

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

Other System Modifications

This Ransomware adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\{8 random characters}
{8 random characters} = {hex values}

HKEY_CURRENT_USER\Software\{8 random characters}
{8 random characters} = {hex values}

Process Termination

This Ransomware terminates the following services if found on the affected system:

  • *backup*
  • *sql*
  • AcronisAgent
  • AcrSch2Svc
  • acrsch2svc*
  • apach*
  • ARSM
  • backup*
  • cbvscserv*
  • dc*32
  • firebird*
  • hMailServer
  • IASJet
  • IBM Domino*
  • ibmiasrw
  • IISADMIN
  • Lotus*
  • MMS
  • mr2kserv
  • MSExchange*
  • omsad
  • QB*
  • QuickBooksDB*
  • server Administrator
  • ShadowProtectSvc
  • Simply Accounting Database Connection Manager
  • SP*4
  • SPXService
  • sql*
  • stc_endpt_svc
  • StorageCraft ImageManager
  • teamviewer
  • veeam*
  • vsnapvss
  • wbengine
  • wrsvc

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

  • *sql*
  • agent*
  • agntsvc.exe
  • apach*
  • b1*
  • ba*
  • bd2*
  • be*
  • bes10*
  • black*
  • cbservi*
  • cbvscserv*
  • cfdot*
  • coldfus*
  • db*
  • dbeng50.exe
  • dbsnmp.exe
  • encsvc.exe
  • excel.exe
  • fdlaunch*
  • firefoxconfig.exe
  • hMailServer*
  • IBM*
  • infopath.exe
  • jetty.exe
  • msaccess.exe
  • msdtssr*
  • msmdsrv*
  • mspub.exe
  • mydesktopqos.exe
  • mydesktopservice.exe
  • nservice.exe
  • nslsvice.exe
  • ntrtscan.exe
  • ocautoupds.exe
  • ocomm.exe
  • ocssd.exe
  • onenote.exe
  • oracle*
  • oracle.exe
  • outlook.exe
  • pg*
  • postg*
  • powerpnt.exe
  • QB*
  • report*
  • sage*
  • sap*
  • sqbcoreservice.exe
  • sql*
  • store.exe
  • swag*
  • swstrtr*
  • synctime.exe
  • tbirdconfig.exe
  • team*
  • thebat.exe
  • thebat64.exe
  • thunderbird.exe
  • vee*
  • visio.exe
  • wbengine*
  • winword.exe
  • wordpad.exe
  • wrsa.exe
  • xfssvccon.exe

Other Details

This Ransomware adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\{8 random characters}

HKEY_CURRENT_USER\Software\{8 random characters}

Ransomware Routine

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

  • autorun.inf
  • boot.ini
  • bootfont.bin
  • bootmgr
  • bootnxt
  • bootsect.bak
  • desktop.ini
  • gdipfont*.dat
  • iconcache.db
  • ntldr
  • ntuser.dat
  • ntuser.dat*
  • ntuser.ini
  • thumbs.db
  • usrclass.dat
  • usrclass.dat*

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

  • *$windows.~ws
  • *:\program file*\vmwaree
  • *:\users\*\*tempmp
  • *:\users\*\appdata\*\microsoftsoft"
  • *:\windows"
  • *:\winnt"
  • *\program file*\common files\*shareded
  • *\program file*\common files\reference ass*s*
  • *\program file*\common files\systemem
  • *\program file*\cuass*
  • *\program file*\microsoft gamess
  • *\program file*\vmwaree
  • *\program file*\windows media*
  • *\program file*\windows ntt
  • *\program file*\windows photo*
  • *\program file*\windows portable*
  • *\program file*\windows side*
  • *\program file*\windowspowershelll
  • *\windows\cache**"
  • *appdata*microsoft
  • *appdata*packages
  • *boot
  • *dvd maker
  • *Internet Explorer
  • *media player
  • *microsoft\provisioning
  • *Mozilla
  • *Mozilla*
  • *msocache
  • *Old Firefox data
  • *perflogs
  • *system volume information
  • *temporary internet*
  • *windows defender
  • *windows.old
  • \*\users\*\*temptemp"
  • \*\users\*\appdata\*\microsoftrosoft
  • \*\windowsws
  • \*\winntnt"

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

  • .{6 random characters}

It drops the following file(s) as ransom note:

  • {Encrypted Directory}\{6 random characters}-Readme.txt

It avoids encrypting files with the following file extensions:

  • .386
  • .adv
  • .ani
  • .bat
  • .cab
  • .clb
  • .cmd
  • .com
  • .cpl
  • .cur
  • .deskthemepack
  • .diagcab
  • .diagcfg
  • .diagpkg
  • .dll
  • .drv
  • .exe
  • .hlp
  • .hta
  • .icl
  • .icns
  • .ico
  • .ics
  • .idx
  • .key
  • .ldf
  • .lnk
  • .lock
  • .mod
  • .mpa
  • .msc
  • .msi
  • .msp
  • .msstyles
  • .msu
  • .mui
  • .nls
  • .nomedia
  • .ocx
  • .prf
  • .ps1
  • .regtrans-ms
  • .rom
  • .rtp
  • .scr
  • .shs
  • .spl
  • .sys
  • .theme
  • .themepack
  • .wpx

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.852.08
FIRST VSAPI PATTERN DATE: 06 May 2020
VSAPI OPR PATTERN File: 15.853.00
VSAPI OPR PATTERN Date: 07 May 2020

Step 1

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 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

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_LOCAL_MACHINE\SOFTWARE\{8 random characters}
    • {8 random characters} = {hex values}
  • In HKEY_CURRENT_USER\Software\{8 random characters}
    • {8 random characters} = {hex values}

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_LOCAL_MACHINE\SOFTWARE\{8 random characters}
    • (null)
  • In HKEY_CURRENT_USER\Software\{8 random characters}
    • (null)

Step 5

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.
  • {Encrypted Directory}\{6 random characters}-Readme.txt
  • %User Temp%\{random characters}-.tmp
  • %User Temp%\{random characters}-.0.cs
  • %User Temp%\{random characters}-.dll
  • %User Temp%\{random characters}-.cmdline
  • %User Temp%\{random characters}-.out
  • %User Temp%\{random characters}-.err
  • %User Temp%\{random characters}-.pdb
  • %User Temp%\{random characters}.tmp
  • %User Temp%\{random characters}.0.cs
  • %User Temp%\{random characters}.dll
  • %User Temp%\{random characters}.cmdline
  • %User Temp%\{random characters}.out
  • %User Temp%\{random characters}.err
  • %User Temp%\{random characters}.pdb

Step 6

Scan your computer with your Trend Micro product to delete files detected as Ransom.PS1.NETWALKER.B. 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 7

Restore encrypted files from backup.


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