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Welcome back.

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And by now we already got two options that we coded the third option that we should do right now is

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the changing of the directory.

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If you simply just run our server right here and you run the backdoor

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you can execute all of the commands of course such as in my class and all of the other comments you

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can execute in the terminal.

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If I type BW DB It will give me my current working directory or the directory in which I'm currently

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in inside of this program and it is inside of our back or project.

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But if we for example want to go one directory back inside of the pie chart projects inside of a terminal

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our regular commands will be C D and then two dots.

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But if you press here enter and you type BW D once again you will still be the back door directory.

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Therefore these C D command doesn't really work for now.

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So we need to code it inside of our program.

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Let's quit this and let's go to our server and backdoor.

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Let's add another option below clear else if command equals equals C D.

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And then space.

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Now make sure that you add this space because C D and C the Space Command are not the same especially

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in Windows.

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If in Windows you type C D it will print to the current working directory but if you type C D and then

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the directory name it will change the directory into the directory that you specified.

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So by telling our server that if the command equals C D and then empty space that means that after this

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will come the directory name and that we want to change the directory therefore inside of our server.

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All we want to do is we want to pass.

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We don't really want to get any result back such as here because there is nothing really to be printed

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out once you are switching the directories.

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There is nothing really as an output but inside of our backdoor we need to execute the directory switching.

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So right here if I type else if command equals equals to see these and then empty space then we want

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to use the OS library to change directory and luckily inside of the OS library we get a function which

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is called C H there.

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And before we actually continue with this function we need to import os inside of our backdoor so we

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can use that function.

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And let's go down here.

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The OS change directory function takes one argument and that is the directory that we want to change

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too.

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So how can we specify the directory.

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Well we know that the command will look something like this.

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So let's type it right here.

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The command will be something like this C deep desktop the first three characters are what we are specifying

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right here.

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So these are the first street characters.

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Therefore what we can do we can simply just compare LC command.

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And then first three characters which we specify by opening square brackets and then typing two dots

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up to three.

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That means we are comparing on the first three characters if they're equal to this then we can change

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the directory of the rest of the comment so we can change the directory of the command and then three

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characters and from there.

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What this means is we are going to compare this part and if it is equal to C D and then empty space

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then we are going to perform the OS not change directory onto this part which will change the directory

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to the desktop directory.

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Otherwise this will not work if we don't specify it like this.

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First of all let's delete this and we need to add the same thing inside of our server.

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So what we are comparing right here is we are comparing first three characters let's see whether this

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will work.

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This is all we need to specify in order to change the directory and now we can test it out.

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So Python 3 server and let's from the backdoor once again if I type P WD to check my current working

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directory we are in the backdoor directory let's go on the rectory back to C D and then two dots and

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then I type P.W. WD once again and now it seems to work we are in the slash root slash by and project

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directory if I type unless we should see all of our previous projects as we can see them right here.

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Good.

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Now we can change the directories we can go to the one scanner if we want to and we can check the contents

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of the bone scan or directory so we successfully coded the C D function or the changing of the directory

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option to our backdoor and now we are ready to proceed on to the next option which is going to be the

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uploading of the files to the target machine.

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Okay.

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So thank you for watching this tutorial and I will see you in the next lecture by.