Ransom.Win32.STOP.AF

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 downloads a file from a certain URL then renames it before storing it in the affected system.

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%\{Hash of Machine GUID}\{malware file name}.exe

It adds the following processes:

• "%AppDataLocal%\{Hash of Machine GUID}\{Executed Malware FileName}.exe" --ForNetRes "agkNQJrejDgKq2u1fjIftdGCN4suWAg6bb8Pqit2" 1OcNMvbG9a2vBz0BdsXRX88kjuVX9ku4EmR64St1 IsNotAutoStart IsTask -> Execute the malware that is not an autostart but a task
• "%AppDataLocal%\{Hash of Machine GUID}\{Executed Malware FileName}.exe" --Service {PID of the Parent Malware Running} "agkNQJrejDgKq2u1fjIftdGCN4suWAg6bb8Pqit2" 1OcNMvbG9a2vBz0BdsXRX88kjuVX9ku4EmR64St1
• "{Executed Malware File Path}\{Executed Malware File Name}.exe" --Task -> Executes the malware as a task
• "%AppDataLocal%\{Hash of Machine GUID}\{Executed Malware FileName}.exe" --Service {New PID of the Parent Malware Running} "agkNQJrejDgKq2u1fjIftdGCN4suWAg6bb8Pqit2" 1OcNMvbG9a2vBz0BdsXRX88kjuVX9ku4EmR64St1
• icacls "%AppDataLocal%\{Hash of Machine GUID}" /deny *S-1-1-0:(OI)(CI)(DE,DC)

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

It creates the following folders:

• %AppDataLocal%\{Hash of Machine GUID}
• %AppDataLocal%\{GUID of the Malware File}

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

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

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

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%\{Hash of Machine GUID}\{Malware File Name}.exe" --AutoStart"

Download Routine

This Ransomware downloads files from the following URLs then renames them before storage in the affected system:

• http://{BLOCKED}t.ug/tesptc/penelop/3.exe
• http://{BLOCKED}t.ug/tesptc/penelop/4.exe
• http://{BLOCKED}t.ug/tesptc/penelop/5.exe

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}t.ug/6454hgvghfgtyryfgfgvcvsydtfystdsbvdfpenelop/sdfsvfbvsbdfdfgdfhfgserwcv/get.php?pid=07681C37D9C280E24A62211D2ECCD4F4
• Connects to the following url to download its updated verion:
  
  • http://{BLOCKED}t.ug/tesptc/penelop/updatewin.exe
  • http://{BLOCKED}t.ug/tesptc/penelop/updatewin1.exe
  • http://{BLOCKED}t.ug/tesptc/penelop/updatewin2.exe
• Checks if there is an existing copy of itself in %AppDataLocal% then delete it and drops a copy of itself at %AppDataLocal%
• Adds the following Scheduled Task:
  
  • Task Name: Time Trigger Task
  Schedule: Starts at 1:20 PM on 11/1/2018 - after triggered repeat every 5 mins. Trigger expires at 5/2/2020 8:00 AM
  Task to be run: "%AppDataLocal%\{Hash of Machine GUID}\{Malware File Name}.exe"
• It accepts the following arguments:
  
  • --Admin -> run the malware as admin
  • --AutoStart -> Creates an Auto Start mechanism using registry keys to execute the malware.
  • --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 -> Execute malware as a task
  • IsNotTask -> Execute malware not as a task

Ransomware Routine

This Ransomware avoids encrypting files found in the following folders:

• C:\$Recycle.Bin\
• C:\PerfLogs\
• C:\$WINDOWS.~BT\
• C:\dell\
• C:\Intel\
• C:\MSOCache\
• C:\Games\
• C:\Windows.old\
• %AppDataLocal%
• %Application Data%
• %Windows%
• %ProgramData%\Microsoft\
• %ProgramData%\Package Cache\
• %ProgramData%\Desktop\
• %Public%
• %Program Files% ; (for both 32 and 64 bit OS)
• {Logical Drive Letter}\Users\%username%\AppData\Roaming\
• {Logical Drive Letter}\Users\%username%\AppData\Local\
• {Logical Drive Letter}\Windows\
• {Logical Drive Letter}\PerfLogs\
• {Logical Drive Letter}\ProgramData\Desktop\
• {Logical Drive Letter}\ProgramData\Microsoft\
• {Logical Drive Letter}\ProgramData\Package Cache\
• {Logical Drive Letter}\Users\Public\
• {Logical Drive Letter}\$Recycle.Bin\
• {Logical Drive Letter}\$WINDOWS.~BT\
• {Logical Drive Letter}\dell\
• {Logical Drive Letter}\Intel\
• {Logical Drive Letter}\MSOCache\
• {Logical Drive Letter}\Program Files\
• {Logical Drive Letter}\Program Files (x86)\
• {Logical Drive Letter}\Games\

(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local on Windows Vista, 7, and 8.. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, and 8.. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.. %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData in Windows Vista, 7, and 8.. %Public% is the folder that serves as a repository of files or folders common to all users, which is usually C:\Users\Public in Windows Vista, 7, and 8.. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), 7 (32-bit), and 8 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), 7 (64-bit), and 8 (64-bit).)

It renames encrypted files using the following names:

• {encrypted file}.norvas

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

• {Encrypted Directory}\_readme.txt