how to close connections?

**user222** · 04-02-2005

Is there something that can close an established connections? I need it when a hacker hacks into my computer.

**junme** · 04-02-2005

1 a pair of wire cutters on your modem line
2 the off button in your computer

**user222** · 04-02-2005

Originally Posted by junme

1 a pair of wire cutters on your modem line
2 the off button in your computer

I meant a command line or graphical utility, like Sysinternals's TCPView for Windows.

**logan5** · 04-02-2005

Most any firewall will allow you to stop all traffic (to and from) your computer. You don't say what distro you are using, but I would assume that they all have a stock firewall. Or look at something like firestarter or smoothwall.

Or you can shut down the ethernet card by opening a terminal and doing

Code:

ifdown eth0

Change the 0 (zero) in eth0 to what every interface you have active at the time.

If you want to bring it back up do

Code:

ifup eth0

Note: you will probably need to be root to do this

**jeickal** · 04-02-2005

Shutting down the ethernet interface is kinda brutal, yet efficient I admit....
But if you need to keep browsing while ending an intruder's connection to your PC, besides using a firewall as logan5 suggested there is another indirect way:
Add a static route pointing to his IP redirecting the traffic to localhost. This way the packets sent from the cracker's PC will reach your PC but he will never get anything back (since the return path is pointing to localhost). If you dont make the route persistant it will go away at the next reboot.

OK I know, it's not as having a command to end the connection like you were asking, but it has an advantage: The bad guy will believe you disconnected your computer from the network, since he will never get any answer back. If you find a way to end its connection, he could start over a second after you disconnected him, and even DoS you.

**zeeone** · 04-04-2005

Or you could reach over and turn off your modem.

**sdousley** · 04-04-2005

logan5, i am not too sure as to how well this will work (unless u leave it down for a short while. When i ssh into my server and run

Code:

/etc/init.d/network restart

the ssh session doesn't die, and i am still connected. So i would suggest stoppin network for 5 mins so a timeout can occur on the 'hacker' before bringing back up.

**jeickal** · 04-04-2005

Originally Posted by user222

Is there something that can close an established connections? I need it when a hacker hacks into my computer.

I found a small program called "hunt" that looks like it has the ability to reset TCP connections.
I didn't have time to try it yet. But the description looks interesting:
==> http://lin.fsid.cvut.cz/~kra/index.html

**scm** · 04-05-2005

If you know what process the cracker (not hacker, please!) is connected to, just "kill -9 <pid>" it (where <pid> is that process's ID).

**user222** · 04-06-2005

Is there something like TCPView for Windows that runs on Linux? It shows the active connections graphically, and it could also close active connections.

this is what it looks like:
http://www.2and2.net/Uploads/Images/tcpview_win.gif

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