Ransom.Win32.STOP.AN

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 saves downloaded files into the said created folder. As of this writing, the said sites are inaccessible.

It drops files as ransom note.

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%\{GUID}\{malware file name}.exe

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

It drops the following files:

• %System Root%\SystemID\PersonalID.txt

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

It adds the following processes:

• icacls "%AppDataLocal%\{GUID}" /deny *S-1-1-0:(OI)(CI)(DE,DC)
• "{Executed Malware File Path}\{Executed Malware File Name}.exe" --Admin- IsNotAutoStart IsNotTask ← malware is executed as Admin and not executed as autorun registry or via task

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

It creates the following folders:

• %System Root%\SystemID
• %AppDataLocal%\{GUID} ← created two(2) folders, one(1) for drop copy and one(1) for downloaded files.

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

• {FBB4BCC6-05C7-4ADD-B67B-A98A697323C1}
• {1D6FC66E-D1F3-422C-8A53-C0BBCF3D900D}

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
SysHelper = ""%AppDataLocal%\{GUID}\{Malware File Name}.exe" --AutoStart"

Other System Modifications

This Ransomware adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
SysHelper = 1

Download Routine

This Ransomware connects to the following website(s) to download and execute a malicious file:

• http://{BLOCKED}ug/files/cost/updatewin.exe
• http://{BLOCKED}ug/files/cost/updatewin1.exe
• http://{BLOCKED}ug/files/cost/updatewin2.exe
• http://{BLOCKED}ug/files/cost/3.exe
• http://{BLOCKED}ug/files/cost/4.exe
• http://{BLOCKED}ug/files/cost/5.exe

It saves downloaded files into the said created folder.

As of this writing, the said sites are inaccessible.

Other Details

This Ransomware does the following:

• Connects to the URL to get the arguments needed for the "--Service" and "--ForNetRes" to perform it's routine:
  
  • http://{BLOCKED}ug/vbcbcvbcbv51/dgdgdfgd/get.php?pid={Hash PID}&first={true|false}
• Adds the following Scheduled Task:
  
  • Task Name: Time Trigger Task
  Schedule: Once, after triggered repeat every 5 mins. Trigger expires at 5/2/2030 8:00 AM
  Task to be run: "%AppDataLocal%\{GUID}\{Malware File Name}.exe"
• It accepts/ add the following arguments to check its execution:
  
  • --Admin -> run the malware as admin
  • --AutoStart -> executes using autorun registry keys.
  • --ForNetRes {Argumet from the URL} {Argument From the URL}
  • --Service {PID of the Parent Malware Running} {Argumet from the URL} {Argument From the URL}
  • IsAutoStart -> Execute malware as an autostart
  • IsNotAutoStart -> Execute malware not as an autostart
  • IsTask/Task -> Execute malware as a task
  • IsNotTask -> Execute malware not as a task
• It connects to the following URL(s) to get the affected system's IP address and location:
  • https://{BLOCKED}i.{BLOCKED}p.ua/geo.json
    • It terminate and delete itself on the affected sysyem if the return of the IP address location are the following:
      • RU (Russia)
      • BY (Belarus)
      • UA (Ukraine)
      • AZ (Azerbaijan)
      • AM (Armenia)
      • TJ (Tajikistan)
      • KZ (Kazakhstan)
      • KG (Kyrgyzstan)
      • UZ (Uzbekistan)
      • SY (Syrian Arab Republic)

Ransomware Routine

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

• ntuser.dat
• .sys
• .bat
• .dll
• .lnk
• .ini
• _readme.txt
• .DLL
• .blf
• ntuser.dat.LOG1
• ntuser.dat.LOG2
• ntuser.pol
• .regtrans-ms

It avoids encrypting files found in the following folders:

• C:\Users\Public\
• C:\SystemID\
• C:\Users\Default User\
• C:\Users\Public\
• C:\Users\All Users\
• C:\Users\Default\
• C:\Documents and Settings\
• C:\ProgramData\
• C:\Recovery\
• C:\System Volume Information\
• C:\Users\%username%\AppData\Roaming\
• C:\Users\%username%\AppData\Local\
• C:\Windows\
• C:\PerfLogs\
• C:\ProgramData\Microsoft\
• C:\ProgramData\Package Cache\
• C:\Users\Public\
• C:\$Recycle.Bin\
• C:\$WINDOWS.~BT\
• C:\dell\
• C:\Intel\
• C:\MSOCache\
• C:\Program Files\
• C:\Program Files (x86)\
• C:\Games\
• C:\Windows.old\
• D:\Users\%username%\AppData\Roaming\
• D:\Users\%username%\AppData\Local\
• D:\Windows\
• D:\PerfLogs\
• D:\ProgramData\Desktop\
• D:\ProgramData\Microsoft\
• D:\ProgramData\Package Cache\
• D:\Users\Public\
• D:\$Recycle.Bin\
• D:\$WINDOWS.~BT\
• D:\dell\
• D:\Intel\
• D:\MSOCache\
• D:\Program Files\
• D:\Program Files (x86)\
• D:\Games\
• E:\Users\%username%\AppData\Roaming\
• E:\Users\%username%\AppData\Local\
• E:\Windows\
• E:\PerfLogs\
• E:\ProgramData\Desktop\
• E:\ProgramData\Microsoft\
• E:\ProgramData\Package Cache\
• E:\Users\Public\
• E:\$Recycle.Bin\
• E:\$WINDOWS.~BT\
• E:\dell\
• E:\Intel\
• E:\MSOCache\
• E:\Program Files\
• E:\Program Files (x86)\
• E:\Games\
• F:\Users\%username%\AppData\Roaming\
• F:\Users\%username%\AppData\Local\
• F:\Windows\
• F:\PerfLogs\
• F:\ProgramData\Desktop\
• F:\ProgramData\Microsoft\
• F:\Users\Public\
• F:\$Recycle.Bin\
• F:\$WINDOWS.~BT\
• F:\dell\
• F:\Intel\

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

• .cosakos

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

• {Encrypted File Directory}\_readme.txt