Saturday, February 14, 2009

Ethical Hacking through Windows XP for Computer Security

Ethical Hacking through Windows XP for Computer Security

Part I: The Magic of DOS
In this guide you will learn how to telnet , forge email, use
nslookup and netcat with Windows XP.
So you have the newest, glitziest, "Fisher Price" version of Windows: XP. How can you use XP in a way that sets you apart from the boring millions of ordinary users?
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Luser Alert: Anyone who thinks this GTMHH will reveal how to blow up people's TV sets and steal Sandra Bullock's email is going to find out that I won't tell them how.
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The key to doing amazing things with XP is as simple as D O S. Yes, that's right, DOS as in MS-DOS, as in MicroSoft Disk Operating System. Windows XP (as well as NT and 2000) comes with two versions of DOS. Command.com is an old DOS version. Various versions of command.com come with Windows 95, 98, SE, ME, Window 3, and DOS only operating systems.
The other DOS, which comes only with the XP, 2000 and NT operating systems, is cmd.exe. Usually cmd.exe is better than command.com because it is easier to use, has more commands, and in some ways resembles the bash shell in Linux and other Unix-type operating systems. For example, you can repeat a command by using the up arrow until you back up to the desired command. Unlike bash, however, your DOS command history is erased whenever you shut down cmd.exe. The reason XP has both versions of DOS is that sometimes a program that won?t run right in cmd.exe will work in command.com
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Flame Alert: Some readers are throwing fits because I dared to compare DOS to bash. I can compare cmd.exe to bash if I want to. Nanny nanny nah nah.
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DOS is your number one Windows gateway to the Internet, and the open sesame to local area networks. From DOS, without needing to download a single hacker program, you can do amazingly sophisticated explorations and even break into poorly defended computers.
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You can go to jail warning: Breaking into computers is against the law if you do not have permission to do so from the owner of that computer. For example, if your friend gives you permission to break into her Hotmail account, that won't protect you because Microsoft owns Hotmail and they will never give you permission.
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You can get expelled warning: Some kids have been kicked out of school just for bringing up a DOS prompt on a computer. Be sure to get a teacher's WRITTEN permission before demonstrating that you can hack on a school computer.
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So how do you turn on DOS?
Click All Programs -> Accessories -> Command Prompt
That runs cmd.exe. You should see a black screen with white text on it, saying something like this:
Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.
C:\>
Your first step is to find out what commands you can run in DOS. If you type "help" at the DOS prompt, it gives you a long list of commands. However, this list leaves out all the commands hackers love to use. Here are some of those left out hacker commands.
TCP/IP commands:
telnet
netstat
nslookup
tracert
ping
ftp
NetBIOS commands (just some examples):
nbtstat
net use
net view
net localgroup
TCP/IP stands for transmission control protocol/Internet protocol. As you can guess by the name, TCP/IP is the protocol under which the Internet runs. along with user datagram protocol (UDP). So when you are connected to the Internet, you can try these commands against other Internet computers. Most local area networks also use TCP/IP.
NetBIOS (Net Basic Input/Output System) protocol is another way to communicate between computers. This is often used by Windows computers, and by Unix/Linux type computers running Samba. You can often use NetBIOS commands over the Internet (being carried inside of, so to speak, TCP/IP). In many cases, however, NetBIOS commands will be blocked by firewalls. Also, not many Internet computers run NetBIOS because it is so easy to break in using them. We will cover NetBIOS commands in the next Guide to XP Hacking.

How to Telnet with Windows XP
The queen of hacker commands is telnet. To get Windows help for
telnet, in the cmd.exe window give the command:
C:\>telnet /?
Here's what you will get:
telnet [-a][-e escape char][-f log file][-l user][-t term][host
[port]]
-a Attempt automatic logon. Same as -l option except uses
the currently logged on user's name.
-e Escape character to enter telnet client prompt.
-f File name for client side logging
-l Specifies the user name to log in with on the remote system.
Requires that the remote system support the TELNET ENVIRON
option.
-t Specifies terminal type.
Supported term types are vt100, vt52, ansi and vtnt only.
host Specifies the hostname or IP address of the remote computer
to connect to.
port Specifies a port number or service name.
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Newbie note: what is a port on a computer? A computer port is sort of like a seaport. It's where things can go in and/or out of a computer. Some ports are easy to understand, like keyboard, monitor, printer and modem. Other ports are virtual, meaning that they are created by software. When that modem port of yours (or LAN or ISDN or DSL) is connected to the Internet, your computer has the ability to open or close any of over 65,000 different virtual ports, and has the ability to connect to any of these on another computer - if it is running that port, and if a firewall doesn?t block it.
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Newbie note: How do you address a computer over the Internet? There are two ways: by number or by name.
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The simplest use of telnet is to log into a remote computer. Give the
command:
C:/>telnet targetcomputer.com (substituting the name of the computer you want to telnet into for targetcomputer.com)
If this computer is set up to let people log into accounts, you may
get the message:
login:
Type your user name here, making sure to be exact. You can't swap between lower case and capital letters. For example, user name Guest is not the same as guest.
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Newbie note: Lots of people email me asking how to learn what their user name and password are. Stop laughing, darn it, they really do. If you don't know your user name and password, that means whoever runs that computer didn't give you an account and doesn't want you to log on.
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Then comes the message:
Password:
Again, be exact in typing in your password.
What if this doesn't work?
Every day people write to me complaining they can't telnet. That is
usually because they try to telnet into a computer, or a port on a
computer that is set up to refuse telnet connections. Here's what it
might look like when a computer refuses a telnet connection:
C:\ >telnet 10.0.0.3
Connecting To 10.0.0.3...Could not open connection to the host, on port 23. A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
Or you might see:
C:\ >telnet techbroker.com
Connecting To techbroker.com...Could not open connection to the host, on port 23.
No connection could be made because the target machine actively
refused it.
If you just give the telnet command without giving a port number, it
will automatically try to connect on port 23, which sometimes runs a
telnet server.
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Newbie note: your Windows computer has a telnet client program,
meaning it will let you telnet out of it. However you have to install
a telnet server before anyone can telnet into port 23 on your
computer.
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If telnet failed to connect, possibly the computer you were trying to
telnet into was down or just plain no longer in existence. Maybe the
people who run that computer don't want you to telnet into it.
How to Telnet into a Shell Account
Even though you can't telnet into an account inside some computer, often you can get some information back or get that computer to do something interesting for you. Yes, you can get a telnet connection to succeed -without doing anything illegal --against almost any computer, even if you don't have permission to log in. There are many legal things you can do to many randomly chosen computers with telnet. For example:
C:/telnet freeshell.org 22
SSH-1.99-OpenSSH_3.4p1
That tells us the target computer is running an SSH server, which enables encrypted connections between computers. If you want to SSH into an account there, you can get a shell account for free at
. You can get a free SSH client program from
.
One reason most hackers have shell accounts on Internet servers is because you can meet the real hackers there. When you've logged in, give the command w or who. That gives a list of user names. You can talk to other users with tht talk command. Another fun thing, if your shell account allows it, is to give the command
ps -auxww
It might tell you what commands and processes other users are running. Ask other users what they are doing and they might teach you something. Just be careful not to be a pest!
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You can get punched in the nose warning: Your online provider might kick you off for making telnet probes of other computers. The solution is to get a local online provider and make friends with the people who run it, and convince them you are just doing harmless, legal explorations.
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Sometimes a port is running an interesting program, but a firewall won't let you in. For example, 10.0.0.3, a computer on my local area network, runs an email sending program, (sendmail working together with Postfix, and using Kmail to compose emails). I can use it from an account inside 10.0.0.3 to send emails with headers that hide from where I send things.
If I try to telnet to this email program from outside this computer,
here's what happens:
C:\>telnet 10.0.0.3 25
Connecting To 10.0.0.3...Could not open connection to the host, on
port 25.
No connection could be made because the target machine actively
refused it.
However, if I log into an account on 10.0.0.3 and then telnet from
inside to port 25, here's what I get:
Last login: Fri Oct 18 13:56:58 2002 from 10.0.0.1
Have a lot of fun...
cmeinel@test-box:~> telnet localhost 25
Trying ::1...
telnet: connect to address ::1: Connection refused
Trying 127.0.0.1... [Carolyn's note: 127.0.0.1 is the numerical
address meaning localhost, the same computer you are logged into]
Connected to localhost.
Escape character is '^]'.
220 test-box.local ESMTP Postfix
The reason I keep this port 25 hidden behind a firewall is to keep
people from using it to try to break in or to forge email. Now the
ubergeniuses reading this will start to make fun of me because no
Internet address that begins with 10. is reachable from the Internet.
However, sometimes I place this "test-box" computer online with a
static Internet address, meaning whenever it is on the Internet, it
always has the same numerical address. I'm not going to tell you what its Internet address is because I don't want anyone messing with it. I just want to mess with other people's computers with it, muhahaha. That's also why I always keep my Internet address from showing up in the headers of my emails.
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Newbie note: What is all this about headers? It's stuff at the
beginning of an email that may - or may not - tell you a lot about
where it came from and when. To see full headers, in Outlook click
view -> full headers. In Eudora, click the "Blah blah blah" icon.
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How to Forge Email with Windows XP Telnet
Want a computer you can telnet into and mess around with, and not get into trouble no matter what you do to it? I've set up my
techbroker.com (206.61.52.33) with user xyz, password guest for you to play with. Here's how to forge email to xyz@techbroker.com using
telnet. Start with the command:
C:\>telnet techbroker.com 25
Connecting To Techbroker.com
220 Service ready
Now you type in who you want the message to appear to come from:
helo santa@techbroker.com
Techbroker.com will answer:
250 host ready
Next type in your mail from address:
mail from:santa@techbroker.com
250 Requested mail action okay, completed
Your next command:
rcpt to:xyz@techbroker.com
250 Requested mail action okay, completed
Your next command:
data
354 Start main input; end with .
Newbie note: just means hit return. In case you can't see that little period between the s, what you do to end composing your email is to hit enter, type a period, then hit enter again.
Anyhow, try typing:
This is a test.
.
250 Requested mail action okay, completed
quit
221 Service closing transmission channel
Connection to host lost.
Using techbroker's mail server, even if you enable full headers, the
message we just composed looks like:
Status: R
X-status: N
This is a test.
That's a pretty pathetic forged email, huh? No "from", no date.
However, you can make your headers better by using a trick with the data command. After you give it, you can insert as many headers as you choose. The trick is easier to show than explain:
220 Service ready
helo santa@northpole.org
250 host ready
mail from:santa@northpole.com
250 Requested mail action okay, completed
rcpt to:
250 Requested mail action okay, completed
data
354 Start main input; end with .
from:santa@deer.northpole.org
Date: Mon, 21 Oct 2002 10:09:16 -0500
Subject: Rudolf
This is a Santa test.
.
250 Requested mail action okay, completed
quit
221 Service closing transmission channel
Connection to host lost.
The message then looks like:
from:santa@deer.northpole.org
Date: Mon, 21 Oct 2002 10:09:16 -0500
Subject: Rudolf
This is a Santa test.
The trick is to start each line you want in the headers with one word
followed by a colon, and the a line followed by "return". As soon as
you write a line that doesn't begin this way, the rest of what you
type goes into the body of the email.
Notice that the santa@northpole.com from the "mail from:" command didn't show up in the header. Some mail servers would show both "from" addresses.
You can forge email on techbroker.com within one strict limitation.
Your email has to go to someone at techbroker.com. If you can find any way to send email to someone outside techbroker, let us know, because you will have broken our security, muhahaha! Don't worry, you have my permission.
Next, you can read the email you forge on techbroker.com via telnet:
C:\>telnet techbroker.com 110
+OK <30961.5910984301@techbroker.com> service ready
Give this command:
user xyz
+OK user is known
Then type in this:
pass test
+OK mail drop has 2 message(s)
retr 1
+OK message follows
This is a test.
If you want to know all possible commands, give this command:
help
+OK help list follows
USER user
PASS password
STAT
LIST [message]
RETR message
DELE message
NOOP
RSET
QUIT
APOP user md5
TOP message lines
UIDL [message]
HELP
Unless you use a weird online provider like AOL, you can use these
same tricks to send and receive your own email. Or you can forge email to a friend by telnetting to his or her online provider's email
sending computer(s).

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