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.

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.
Nice. I'm gonna go ahead and make an unnc.bat to undo it.
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 &quot;forward&quot; that port. It will only forward it from the outside world to one IP address. Go check out <a rel="nofollow" href="http://portforward.com/routers.htm">http://portforward.com/routers.htm</a> to help you do that.<br/>
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. <br />
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.
go to Start and click on run and then on cmd and type in IPconfig/all and then find your IP address. :D
that only shows your network ip. to access it from the 'net you need the other one.
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<br />
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.<br />
I used regedit to put temporary COSMOKEY keys on not as harmful
netcat error
My Anti virus (PC Tools) blocked it.
<a rel="nofollow" href="http://www.securityfocus.com/cgi-bin/index.cgi?c=toolcomments&amp;op=display_comments&amp;ToolID=139&amp;expand_all=true&amp;mode=threaded">http://www.securityfocus.com/cgi-bin/index.cgi?c=toolcomments&amp;op=display_comments&amp;ToolID=139&amp;expand_all=true&amp;mode=threaded</a><br/><br/>go there for netcat :D<br/>
nc.exe is a .tmp file, my antivirus got rid of it. and nc.bat is a webpage.
when I click on the files in this Instructable, it tries to download a tmp file.
tell it to save as &quot;all files&quot; then rename it &quot;netcat.exe&quot; or &quot;putty.exe&quot; it did that to me to<sup>are you useing ie8</sup><br/>
if you save it as netcat.exe, then nc.bat wont work(if you use it) you should save it as nc.exe
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"
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?
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 ??
Of course! Please tell me more about your set-up.
Rule no.0 never give away you ip adress on a site that teaches you how to hack
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.
When I downloaded nc.exe it was a .tmp file, so it didn't work. :o
Hey 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.<br/>a &quot;192.168.x.x&quot; is the ip address <em>behind</em> his router. unless you also have the external ip (the one between your isp and you) , you cant do a single thing but hack <strong>your own</strong> router<br/>
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.
i'm pretty sure that he was just joking.
dude, that's ur local ip, so nothing will happen to ur machine, k? mine was, too , at one time. a local ip is only for your home (or office) network.
lol ur point?
I have a question. What is a backdoor anyway?
How is that different from a VNC? Try ultavnc single click. E-mail it to your friend. When he runs it dials home. No worry about IP root files ect ect.
can u tell me where to get it please? and when u email it does ur friend have to do anything else besides downloading it? please reply thankyou
google ultavnc and check out their ultravnc single click. Yes , your friend needs to click on it. It is not a trojan and it will warn your friend that he/she is installing a remote viewing application.
It is different because you have to 'get down and dirty' with netcat, but the VNC takes the fun out of it. To get netcat on, you have to do either a sort of heist thing, or social engineering. With VNC, it is just point-and-click. Kinda boring....

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