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Welcome back.

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Time to start coding our back door.

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So in this video, we're going to start with the base of our program.

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Remember that we must create two different programs, a server and a back door, and it doesn't matter

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with which one we start.

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So let's in this case, start coding the server first.

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We're going to code both of them simultaneously.

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So what I'm going to do is I'm going to open the terminal and remember that we have these tools directory

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from the first project.

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Let us navigate to there.

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And instead of the port scanner, we're going to make another subdirectory inside of here and call this

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back door.

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Then we are going to change the directory to the subdirectory.

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And here we are going to code our tools.

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So, as I said, let's start with server first to do that with type server that be why we open it using

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NENO and here we are going to code our project.

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So what's the first thing that we must do?

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Well, since these two programs are going to communicate with one another, they must establish a connection

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first.

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And we know that we can do that with the help of a socket library.

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So Socket allows us to initiate an Internet connection between two machines.

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So how are we going to do that?

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Well, first thing that we must do and that we also did inside of our ports scanner is we must initiate

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a socket object and I'm going to call my socket object suck inside of the server that way.

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And to initiate it, I will type socket at socket.

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So we're doing this with the help of the socket library.

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And here in the brackets, we want to specify two different parameters socket that av underscore in

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it.

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Cuma socket dot socket underscore string.

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And I know what you're thinking.

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What even are these arguments.

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Well this socketed if underscore it tells our program that we're going to make a connection over IP

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for address and the socket that stream tells of our program that we're going to use the TCP connection.

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So simple as that.

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Now the next thing that we want to do is we want to bind the IP address and the port.

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This is something that we already did inside of our first project.

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So there's nothing really too much to explain right here.

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We just type SOC and use the methods that bind open to and close to Brackett's.

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And the first parameter is going to be the IP address of our Linux machine in my case, if I go and

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check it out.

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This is not one, but 12, so we'll go right here and specify one or two that one that one dot 12 as

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the first parameter.

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And remember, it must be between the quotes.

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Then I will specify comma and port that we are going to use.

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Well, we can just go with Port five five five five.

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Why not?

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It doesn't even matter, to be honest.

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After we do all of this, we find it the IP address with the port and now the next thing that we must

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do is we must start listening for the incoming connections.

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Remember, this was the crucial part in the reverse.

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Chelse, the target executes the payload, but we must listen for the incoming connections.

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And that is exactly what our server program will do.

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It will listen for the connections.

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And once the target executes a payload, they will connect to our server program.

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So to do that, we can first print like this, let us print listening for the incoming connections just

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so we know which part of the program we are.

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And below that we can type SOC dot listen.

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And we are going to specify five in the brackets, meaning that we are going to listen up to five different

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connections.

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OK, so our program will now be stuck on this part until the connection is established.

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Once the target tries to connect back to us, we need to store their connection in a few variables.

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In another sense, we need to store their socket object that we are going to use to communicate with

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the target.

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And we're also going to split that into an IP address.

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So what I'm going to do is I'm going to type target IP.

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These are going to be two separate variables and they're going to be equal to SOC Dot accept.

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And this method is simply just accepting the incoming connection and storing the targets socket object

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right here.

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And the IP address in the second variable.

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Simple as that.

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Once we do that and once the connection is accepted, we can print.

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That target connected and we can add Frumkin and what we're going to do here is we're going to close

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the quote and add a plus sign and then the string of the IP variable.

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And once again, remember, the IP variable will store the IP address of the target.

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So what we are essentially doing right here is we're printing that.

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We got the connection from the target's IP address.

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OK, we need to close one more bracket right here.

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And what we're going to do at the end is we're just going to enter a function called target communication.

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Now, of course, this function doesn't exist and we're going to code it in some future video.

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But for now, let's just leave it right here.

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We successfully created the socket object binded.

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The IP address with the port, will listen for the incoming connections.

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And at the end, we accepted the connection from our target system.

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We're going to leave it at this for now on our server program.

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And let's go to our backorder program.

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Now we need to figure out the code for our backdoor to make it connect to our server, the API.

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So first thing that we're going to do is, of course, to import.

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The socket library then, as in the server program, we need to initiate the socket object and I'm not

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going to call it soccer right here, I'm just going to call it S.

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And here we're going to specify the same parameters.

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Socket dot af underscore it.

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Comma, socket dot soc underscore straight.

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Well, Rudy explained what these are and the only thing that we need to do right here is we need to

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connect to our target machine, but we're not going to use the connect method right here.

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What we are going to do is we are going to call the connection function.

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And of course, this is a function that doesn't exist.

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So one must code it up here.

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Let's define it first to define connection.

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It will take no parameters between the brackets.

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And what we are going to do is we are going to type right here, try, which is the tri statement.

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So it will try to connect to our killing machine.

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And remember, the connect function requires to open and close brackets the same way that the bind function

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does.

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And it also takes two parameters, which the first one is the IP address of the machine that we want

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to connect to.

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So this will be the IP address of this machine once again and the port will be once again the Port five

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five five five because we want to connect to that port since our server program will be listening on

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that port.

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If it manages to connect, we're going to enter our second function, which is going to be called Shell.

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And this shell function also doesn't exist.

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We're going to code it.

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And what will be the purpose of this shell function is executing the comments.

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So for now, we're just going to leave it right here and we're going to code it later.

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Once we leave the shell function, we can close the socket object.

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And in the accept statement, we can call again this connection function.

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Now, you might be wondering, why are we doing this?

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Well, if I had something like this right here.

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So I go and type while true, which is to remember the infinite loop, and I tap all of these commands

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once so they can belong to the wild Trouillot.

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And right here, I'm going to also add a statement, time to sleep and give me just one second.

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I will explain why I'm doing this.

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Let me just call the function till the end.

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I'll break right here and I will import the time library because we are going to need it since we use

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it right here.

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So what are we doing right here?

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We're calling the connection function.

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This connection function starts and infinite while loop, this infinite loop sleeps for 20 seconds and

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then it tries to connect to our clinics machine.

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If it manages to connect, it will go inside of the shell function where we will execute the comments

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on the target system.

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If it doesn't manage to connect, it will go into this except statement and it will call the same function

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once again.

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So what does this tell you?

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It will run this function infinitely until it manages to connect.

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So this is good because one reason we don't want our target to start the payload and not be able to

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connect just because we haven't started the server yet.

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We want to be able to connect to the target system whenever we want.

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So this function will tell the payload to try to connect to every 20 seconds, every 20 seconds while

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their machine is running.

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This program will try to connect our Kleenex machine so we can start the server at any point of time.

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And after 20 seconds, it will establish a connection to us.

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So this is just calling this function over and over again until this line right here works and they

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connect to us.

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Then we enter a second function, which is the shell function.

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OK, this is the base of our Back-Door DCPI, here is how we are going to connect to our server and

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in the next video, we're going to see what we are going to do with the contents of the shell function.

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And if I save this controller and also the target communication function.

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So these are the functions that will receive and execute commands.

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Feel free to post any question if you have about the code, if there is something that you do not understand.

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And in the next lecture, we are going to continue with the coding of our programs.

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So there.