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This instructable shows you how to create a backdoor on a computer with netcat! I will show you two ways to do this, with and without my batch file that automates it for you. This instructable already assumes that you have already got root permissions on the computer, probably with a 0phcrack LiveCD here. Now, onto the instructable.
 
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Step 1: Download netcat

I have saved you the trouble of 3 minutes of searching Google and have put nc.exe up on instructables for you to download. Optionally, you can also download nc.bat which is a batch file I have created to automate the process for you. Make sure that if you download nc.bat it is 464 bytes, because I kept on uploading versions and finding out something was wrong with it. If it is not 464 bytes, the program will not correspond with this instructable.
nc.exe60 KB
nc.bat464 bytes

Step 2: With nc.bat

First, both files must be in the same directory for nc.bat to work properly. I suggest using a flash drive, or CD-ROM for this operation. I used a 512 mb geek squad flash drive for this, but that is just me. So, copy the files onto your external media device, and bring them to the computer that you have root on. Get on the media device and double-click nc.bat. This will copy the nc.exe file to the system32 folder, in the system root (usually C:\Windows or C:\WINNT) and make the necessary changes to the registry. Then write down the IP address. It will be something like '192.168.1.103', which is mine. Once this is done, reboot the machine and login. Then the anti-virus program may ask you if you want to allow/disallow the program. Click on 'Allow' or similar. Keep in mind that in this instructable, you can only telnet in from the local network of that computer. Then leave, or log off, or whatever else you want.
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locofocos6 years ago
Nice. I'm gonna go ahead and make an unnc.bat to undo it.
duct tape (author)  locofocos6 years ago
cool
Here's my idea. Go under your home router and enable forwarding of nc.exe on port 4444, then you could access the computer from any internet connection. I've got two computers, but my old laptop doesn't like our network, probably cause it has windows and linux on it.... If I look at all the computers on the network, it appears (when it's turned on and hooked up to the router), but not it's shared files (they are turned on to share, i'm not an idiot). If I try to see any other computers on the network from this computer, I can't see any. It's kinda like a one-way mirror. It can connect to the internet fine, but not the network. It's set up just like my desktop. Obviously, netcat won't work.
could you explain how to do that?
Before I tell you how to do it, let me go ahead and tell you that if you do it, ANYONE who has internet (millions of people) could log into your computer and control it, so I would REALLY recommend not doing it, even to someone else's computer. With that being said, you need to forward port 4444. Your router acts as a firewall that blocks people from connecting to you that shouldn't be. If you want to communicate with the outside world, you have to tell your router you want to "forward" that port. It will only forward it from the outside world to one IP address. Go check out http://portforward.com/routers.htm to help you do that.
duct tape (author)  locofocos4 years ago
you might want to set up some sort of login to the machine so that anonymous entry is harder. An IP logger would be another good addition.
duct tape (author)  locofocos6 years ago
that is strange. you went to whatismyip.org or something similar to find the IP address first, right?
Yeah. I'm not saying I've actually done it, but it should work.
duct tape (author)  locofocos6 years ago
k
go to Start and click on run and then on cmd and type in IPconfig/all and then find your IP address. :D
duct tape (author)  paozie6 years ago
that only shows your network ip. to access it from the 'net you need the other one.
jund44 years ago
Hi can anyone tell how to use netcat on internet cuz i tried manytime but it didnt work.It works fine on lan network.so plz help.Thanks
duct tape (author)  jund44 years ago
You need to know the external IP address of the target computer, and then set up the router so that it forwards all requests on the port you are using to the target. It should then be accessible through the internet.
GOOD
I used regedit to put temporary COSMOKEY keys on not as harmful
netcat error
NetDex4 years ago
My Anti virus (PC Tools) blocked it.
teh_noob4 years ago
teh_noob5 years ago
SUPER AWESOME 'IBLE!
pedro_331655 years ago
nc.exe is a .tmp file, my antivirus got rid of it. and nc.bat is a webpage.
admiral0015 years ago
when I click on the files in this Instructable, it tries to download a tmp file.
tell it to save as "all files" then rename it "netcat.exe" or "putty.exe" it did that to me toare you useing ie8
B.F.L.M hg3415 years ago
if you save it as netcat.exe, then nc.bat wont work(if you use it) you should save it as nc.exe
adaviel5 years ago
If you got here via google "download netcat", see the comments on "intro". nc.bat creates a backdoor on your computer if you run it.
-d is for stealth which will make the program run in backgraound and -t is for telnet mode it allows other machine to telnet to it
im having trouble how do you use the window that pops up after you open PuTTY?
and about 15 sec after i open the window it says "connection timmed out"
wee_man5 years ago
Yea hi if i port forwarded port 4444 to a computer on my network could i remotely access it from a computer off my network?
duct tape (author)  wee_man5 years ago
Yes. But I'd put a password or something on it. You would also need a static ip or a domain name from dyndns.com. What I do sometimes is make my computer into a file server with HFS. Just google it and you will come up with an idea...
yea i have a doman name i auctly have game and webservers and all that stuff running on it umm with this is their a way i can add files like from remote computer > host ??
duct tape (author)  wee_man5 years ago
Of course! Please tell me more about your set-up.
tgfmk25 years ago
Rule no.0 never give away you ip adress on a site that teaches you how to hack
duct tape (author)  tgfmk25 years ago
This isn't the actual ip address - it is the network ip. It doesn't matter if someone knows this, unless they are on your network.
ItsLinaxD5 years ago
When I downloaded nc.exe it was a .tmp file, so it didn't work. :o
Hey 192.168.1.103 is my ip address(or at least it seems so)
i-am going to haaaaack youuuuuuu.
ha you're not as smart as you try to be.
a "192.168.x.x" is the ip address behind his router. unless you also have the external ip (the one between your isp and you) , you cant do a single thing but hack your own router
duct tape (author)  mikemmcmeans5 years ago
I think he was making a joke...
Even with someone's ip you can't easily or readily hack them, a number of measures are in place "out of the box" on nearly every computer used nowadays. Regardless of whether or not they have a firewall, hacking is not as simple as script kiddies would have you believe.
duct tape (author)  MostlyHarmless5 years ago
i'm pretty sure that he was just joking.
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