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Gathering Info on a Host: The Essential Ingredient for getting root
By Ankit Fadia ankit@bol.net.in
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I get a lot of emails from people asking me how they can break into their ISP or how they can break into a system etc etc. Infact, such questions are almost the most common ones, from all the questions I get. Well, after this popular demand, I thought that an entire manual on breaking into systems was needed. So here goes..
You see, breaking into systems or getting root on a system is not as difficult as it seems. And it by no means requires you to be an Uberhacker. Getting into a system is quite easy and it requires you to know at least one programming language (preferably C), and have a more than an average IQ. However, breaking into systems does require a bit of luck and also a bit of carelessness or stupidity on the part of the system administrator of the target system.
What I mean to say by all this is that, breaking into systems is no big deal, anyone could do that, even a script kiddie, however, the part of the entire Hacking process where more than most people falter is the remaining undetected part. Anonymity or remaining anonymous to the Server logs and preventing detection of a break-in is the most difficult part of Hacking into a system.
What separates a good Hacker from a Script Kiddie or a Lamer is that the former has more than several ways of making sure that no one even suspects that there has been a break in, while on the other hand, the later has no clue what so ever as to what he is doing or what he needs to do to prevent such detection. There are so many ready to Use canned C programs or Hacking utilities available on the net, that a huge number of wannabe hackers, download them and use them to Hack into systems. Well, not only do they do not work properly and flawlessly, they also provide no mechanism of remaining anonymous. What is more, say if you are not using a canned Hacking tool, and are also not trying to remain anonymous, then you stand a greater chance of remaining undetected than if you were using such a tool. So think before you use such tools, you might be able to get the Password file and become very kewl, however, you will certainly be caught later if not sooner.
The first step that you need to take once you have decided the target computer is to find out as much information as you can about it. You see, to break into a system you need to exploit a vulnerability existing in the services offered by it. Almost all systems have certain open ports, which have certain daemons or services running on them.
**********************
HACKING TRUTH: There are two types of ports. There are hardware ports, which are the slots existing behind the CPU cabinet of your system, into which you plug-in or connect your hardware to. For Example, COM1, COM2, Parallel Port etc. However, we are not interested in such ports. We are concerned with the other type of ports, which are the virtual or the software ports. Such a virtual port is basically a virtual pipe through which information goes in and out. And all open ports have a service or daemon running on it. A service or a daemon is nothing but the software running on these ports, which provide a certain service to the users who connect to it. For Example, Port 25 is always open on a server handling mails, as it is port where the Sendmail service is running by default.
**********************
So basically the first step in your quest to breaking into a system is to get as much information on it, as you can. Try to get, the list of open ports, the list of services running on the respective open ports and whole lots of other kind of information to which I will come later.
Anyway, so firstly, get a good Port Scanner, preferably stealth and then do a port scan on the target host. Now one thing that you must remember while doing a port scan is the fact that there are various so called ‘stealth’ port scanners around which claim to be undetectable, however most of them are detectable. So instead of using such’ false claims’ port scanners, I suggest you code one on your own.
But why do I need to use a stealth Port Scanner and how can I code my own Port Scanner? Well, the reason as to why you need a stealth port Scanner is that many system administrators log all port scans and records the IP and other information on such attempts, this makes you susceptible to getting caught. In my opinion the best Port Scanners around are those, which send SYN/FIN packets from a spoofed host, making logging useless. Such a port Scanner would be coded in C, but will not run in Windows. This was just an idea, now it is up to you to code it yourself.
Anyway, let me assume that you have got hold of a good ‘impossible to detect’ Port Scanner, now scan the target system for all open ports and record the open lists:
Note: In this manual, I have taken up my ISP as an example target system. It would be foo-barred throughout as xxx.bol.net.in
In my case, I found that the following ports were open:
Port Number Service
21 FTP
23 Telnet
25 SMTP
53 DNS
79 Finger
80 HTTP
110 POP
111 Not Useful
389 Not Useful
512 rlogin
Note: Only a few Port Scanners give you both the open Ports and the services running on them. Most Port Scanners only return the list of Open Ports. This is fine too; as once you get the list of open ports then you can find out the corresponding services running on them, referring to the RFC 1700. It contains the complete list of Port Numbers and the corresponding popularly running services.
Now port scanning takes advantage the 3-stage TCP handshake to
determine what ports are open on the
remote computer. To learn more about the TCP\IP protocol read the
networking manuals that I distribute on
my mailing list.
Tools like SATAN and lots of them more allow you to find out the
list of open ports, the daemon or the service running at each open port and
also the service's vulnerability at the click of a button. You can't call
yourself a hacker if you need some Software, which first of all is not written
by you to do something as lame as a port scan. Well yes I do agree that looking
for open ports manually on a server would take a long time. But what I am
suggesting is that you use a Port Scanning tool, which just gives you a list of
open ports without the list of services and the vulnerabilities. I assure you,
if you try and explore an open port of a remote server manually, you will be
able to learn more about the remote system and also it will give you a taste of
what hacking actually is. If you use a port scanner, which gives you all
details at the click of a button to impress your friends, let me assure you
none of them will be impressed, as I am sure anyone can use SATAN and other
such scanners.
Another thing you need to be careful about before port scanning
your ISP is that most port scanners are very easily detected and can easily be
traced and you have no excuse if you are caught doing a port scan on a host.,
it a sure sign of Hacker Activity. There are many stealth scanners like Nmap,
which claim to be untraceable. But the truth is that they are very much
traceable and they are quite inaccurate as they send only a single packet to
check if a port is open or not. And if the host is running the right kind of
Sniffer software maybe Etherpeek then the Port scan can be easily detected and
the IP of the user logged. Anyway some ISP's are really afraid of Hacking
activities and even at the slightest hint of some suspicious hacking activity
something like Port scanning, they can disable your account. So just be
careful.
************
Evil Hacking Trick: Well try to keep an eye on TCP port 12345, and
UDP port 31337 these are the default
ports for the popular trojans NetBus and BO, respectively
*************
Some ISP's are quite aware of Hacking Activities and are one step
ahead. They may be running some excellent software, which will keep hackers
away. EtherPeek is an excellent example of sniffing software, which can easily
trace users who are port scanning. Nuke Nabber a Windows freeware claims to be
able to block Port Scans. I have not tested it so I can't say for sure. Then
there is another fun program known as
Port
Dumper, which can fake daemon (services) like Telnet, Finger etc. There is also
some software, which will show a weird list of open ports. What I mean by that
is, if you port scan a host running such software, then it will keep showing
random open ports, and you port Scanning Software will go crazy.
Anyway, so
once you get a list of open ports, start analyzing the weak points or the
services which might help us to get more information about the target system
which would prove invaluable to the breaking in process. Try to exploit the
commands or the options available on each open port to either find a
vulnerability, which could be exploited, or some kind of information on the
target system. That is pretty much the only kind of things that we would be
looking for. Now, let me explain how I try to find out such things with the
list of open ports (of my ISP) and services running on them.
Note:
Before proceeding, refer to the table of open ports which we got earlier(of
host xxx.bol.net.in) in the manual and yes, I am starting from Port 79 as if I
start from Port 21, then the manual will become very very short.
It has
Port 79 open or in other words, has finger running, however, almost all Finger
daemon are configured to not return much information about Users, however, let
us try some common Finger exploits which can sometimes very very rarely get you
root.
finger root
finger system
finger
These exploits are very very old and do not work almost 99 times
out of 100. So the Finger port is ruled out.
Now let us move on, in the list of open ports, the HTTP port or
Port 80 is also open, this means that this target system probably maintains a
web site. So let me launch my favorite browser (Internet Explorer, if you are
interested.) and see what they have on their site. Well, actually we are not
even remotely interested in what they have on their site, but what we are
interested in is to see, whether they have the CGI-BIN directory open to public
or not, an dif yes if any of the common CGI exploits, which get you root, work
or not.
So I type in the following in the URL box of my browser:
http://xxx.bol.net.in/cgi-bin
I get the NOT FOUND error message; this probably means that this
system does not support CGI-Scripts. If the CGI-Bin directory had been blocked
from public access, then we would probably have gotten the Forbidden Error
Message.
However, finding out that our target system does have the CGI-Bin
directory cannot be said to be disappointing as the known CGI exploits are
almost primitive and finding out new exploits should be kept out of this
manual.
OK, so Port 80 and Port 79 are ruled out, they neither have any
vulnerability nor do they give any information about the target system. [Well
actually the HTTP port does give us some valuable information, but we will come
to that later.]
Anyway, so let us try Port 21 or the FTP port. Now, there are two
ways of connecting to Port 21 of a host, the first one is to telnet to Port 21
and other one is to use the MS-DOS FTP client. You could choose any of the two
for this section, however, I kind of like the command line FTP client, although
many people say it is lame. Anyway, so I launch up a FTP connection to
xxx.bol.net.in.
C:\windows>ftp xxx.bol.net.in
Connected to xxx.bol.net.in.
220-
220-#*************************************************************
220-# Welcome to
MTNL's ftp site
220-#*************************************************************
220-#
220-# You can upload your
own homepages at this site!!!
220-#
220-# Just login with your
username and upload the HTML pages.
220-# (You can use your
favourite HTML editor as well)
220-#
220-# World will see it at
http://web2.mtnl.net.in/~yourusername/
220-#
220-# So get
going......UNLEASH YOUR CREATIVITY !!!!
220-#
220-#*************************************************************
220-
220 ftp2.xxx.bol.net.in FTP server ready.
We are immediately greeted by the FTP daemon banner, which tells
us that this is the FTP server where, people using MTNL’s (My ISP) Internet
Services, can upload their site. Now, normally FTP daemon banners are more
informative than this one. They usually do give away the name of the Operating
System running and also the FTP daemon running. Well, actually it is the login
prompt of the daemon banner which gives us the Operating System running on
it. Normally, a typical daemon banner,
would have the following Login prompt:
220 xxx2.bol.net.in FTP server (Digital UNIX Version 5.60) ready.
User (bol.net.in:(none)):
Notice the System name in the brackets on the first line. However,
normally almost all FTP daemons are better configured (that is the case in the
example target system: xxx.bol.net.in)and their login prompt is somewhat like
the below:
220 ftp2.xxx.bol.net.in FTP server ready.
User (mail2.bol.net.in:(none)):
See, no Operating System name. However, with the help of some kewl
commands, such systems too can be reveal the OS running on them. However,
before we go on, there is one thing that you have to be clear about. Now, we
had FTP’ed to xxx.bol.net.in, so you normally expect to connect to Port 21 of
xxx.bol.net.in, however that is not true. (Atleast in this case.) If you look
at the daemon banner again, then you would notice that the last line says:
220 ftp2.xxx.bol.net.in FTP server ready.
Now how did that happen? Well, is Port 21 not open on
xxx.bol.net.in ? Well, no and yes. What actually happens is that, Port 21 of
xxx.bol.net.in is open and a daemon there is listening for connections. As soon
as a connection is established, it transfers the control or connected the
visitor to ftp2.xxx.bol.net.in, which is on the same network as xxx.bol.net.in.
Now this, ftp.xxx.bol.net.in system is solely a FTP machine. It has no other
services running. So whatever
information, we gather from such a FTP port is not of xxx.bol.net.in but of
ftp2.bol.net.in. Get it?
Anyway, when you get the login prompt, then login anonymously with
the anonymous as the Username and a false email address as the password.
220 ftp2.xxx.bol.net.in FTP server ready.
User (ftp2.xxx.bol.net.in:(none)): anonymous
331 Guest login ok, send your complete e-mail address as password.
Password: xxx@linux.net
230 User anonymous logged in.
Access restrictions apply.
Even if you have an account at the FTP server into which you plan
to break in, it is always better not to use that pair of Username and Password.
Logging in anonymously has many advantages. Say if you did cause some harm to
the target system and if you use your (Nonanonymous) Username and Password
pair, then if you were not able to edit the server logs you could get into some
serious trouble. [Well actually not much, only say your account might be
disabled. However, it could be worse.]
Ok, you are in, now let us get the FTP client to tell us which
commands are available by typing the help command.
ftp> help
Commands may be abbreviated.
Commands are:
! delete
literal prompt
? debug ls put
append dir mdelete pwd
ascii
disconnect mdir quit
bell get mget quote
binary glob mkdir recv
bye hash mls remotehelp
cd help mput rename
close lcd open rmdir
Uhmmm.,.., none of the
above commands seem to be or sound to be of use to us. So the ‘help’ command
did not reveal any useful commands. However, you see the above list of commands
are commands which are offered by the FTP client and almost more often than
not, the FTP daemon offers a wider array of commands. To get a complete list of
commands offered by the FTP daemon, use the ‘remotehelp’ command:
ftp> remotehelp
214-The following commands are recognized (* =>'s
unimplemented).
USER
PORT STOR MSAM*
RNTO NLST MKD
CDUP
PASS
PASV APPE MRSQ*
ABOR SITE XMKD
XCUP
ACCT
TYPE MLFL* MRCP*
DELE SYST RMD
STOU
SMNT*
STRU MAIL* ALLO
CWD STAT XRMD
SIZE
REIN*
MODE MSND* REST
XCWD HELP PWD
MDTM
QUIT
RETR MSOM* RNFR
LIST NOOP XPWD
214 End of help
Note: To get a single line description of each command, type help
followed by a space and the command of which you want a description.
One thing to remember here is that to execute any command from the
remote FTP commands list you need to make use of the ‘literal’ keyword.
What I mean by that is that all remote
FTP commands have to be preceded by the word ‘literal’. For example, say you
want to execute the remote FTP command: ‘stat’, then you would type:
ftp> literal stat
***************
HACKING TRUTH: According to FTP help, the literal command is described as:
ftp> help literal
literal send
arbitrary ftp command
***************
Anyway, amongst the remote FTP commands, the commands of interest
to us are-: ‘stat’ and ‘syst’. Let us see what they return when executed-:
ftp>literal stat
211- ftp2.xxx.bol.net.in FTP server status:
Version 5.60
Connected to
203.xx.251.198 (203.xx.251.198)
Logged in anonymously
TYPE: ASCII, FORM:
Nonprint; STRUcture: File; transfer MODE: Stream
211- No data connection
211 End of status
Note: The IP address is of xxx.bol.net.in and not your machine.
ftp> literal syst
215 UNIX Type: L8 Version: BSD-198911
Voila, we get the Operating System name running on
ftp2.xxx.bol.net.in. At last some useful information.
Finger and HTTP both failed, what do we do now? Let us turn to the
den of the Buggiest daemon on Earth i.e. Sendmail: Port 25, the SMTP port.
Sendmail is certainly the buggiest daemon on earth; it has the
highest number of known exploits amongst all the daemons. So this probably
should get us through. Let us telnet to Port 25 and find out whether an
exploitable version of Sendmail is running.
C:\windows> telnet xxx.bol.net.in 25
220 xxx.bol.net.in ESMTP Sendmail 8.9.1 (1.1.20.3/27Jun00-0346PM)
Thu, 29 Jun 2000 14:18:12 0530 (IST)
When you telnet to Port 25, then the first thing that you come
across would be a something like the above welcome daemon banner. A daemon
banner is a Hacker’s best friend. It reveals important information about the
host, which proves to be invaluable in breaking into it. It basically tells you
which daemon or service is running on that port and also the version of that
particular service. Like for example, in this case, the Sendmail daemon banner
tells us that ESMTP Sendmail 8.9.1 is running and it also gives us other
information about the host at which this service is running.
Anyway, getting back to the topic, this banner reveals a big
vulnerability existing in the host computer. It tells us that xxx.bol.net.in is
running an old, vulnerable version of Sendmail. The latest version is Sendmail
8.9.4 (correct me if I am wrong.), so this particular version of Sendmail
wouldn’t be without any bugs.
So then what you do is visit PacketStorm or search at your
favorite Hacking stuff related search engine for a C program which demonstrates
how to exploit version 8.9.4 of Sendmail. Now, all this might sound a bit too
simple, well it certainly isn’t, read on for more info.
Now, there are a couple of things that you need to keep in mind
while getting this done. Say, you have found out that the victim runs Sendmail
8.9.4, now you cannot simply break in by running any exploit for this version.
By that what, I mean to say is that, an exploit, which is coded to be executed
on a Linux platform, will not work if you try to compile and run it on a
Windows platform. So basically before you execute the ‘kewl’ exploit program
that you downloaded, you should find out which platform it is meant for and if
you are not running that platform, then you will need to get your gray cells
working.
This is the stage where real hackers are differentiated between
script kiddies, this is when those people who really know something
prevail. Normally say if a exploit is
designed to work on Linux, then if you edit its code and change its header
files (if necessary), then that particular exploit can be made to run on
Windows too. However, there are certain exploits, which simply would not run on
a different OS than it is designed too.
Anyway, let us get back to point. You have edited the exploit code
and made it compatible with your platform. Now what else? Another thing that
you want to keep in mind is the Operating System, which the exploit can
exploit. You see, there are certain exploits, which work only if the victim
system is running a specific Operating System. For Example,
There was once a Sendmail hole, which worked only if the target
System was running Sun OS without which, it simply refused to even work.
So in some cases it becomes necessary, to find out the Operating
System running at the target system. Although not all exploits require the
target system to be running a specific system, but why take a chance. Right?
So basically you should be aware of the following things while
getting a ready to use exploit-:
1.)
The Daemon name and version you are trying to exploit For Example,
Sendmail 8.9.4
2.)
The Operating System at which it is designed to run. (If
necessary)
3.)
The operating System it requires the target system to be running.
(If necessary)
That brings us to as to how to find out the Operating System running
at the target system? Well, the HTTP port holds the key. Simply, telnet to Port
80 of the target system.
C:\windows>telnet xxx.bol.net.in 80
Now, once you get the input prompt, then, type an invalid HTTP
command. For Example, X or Iamgreat or abc etc. Just type anything as long as
it is not a valid HTTP command. Then press enter twice.
***********
Hacking Truth: After each HTTP command one has to press Enter
Twice to send the command to the server or to bring about a response from a
server. It is just how the HTTP protocol works.
**********
On Port 80 of my example target system, I type simply ‘ankit’ and
press enter twice. This is the kind of response I get:
HTTP/1.1 400 Bad Request
Server: Netscape-Enterprise/3.5.1
The server replies with the version of HTTP it is running (not so
important), it gives us an error message and the error code associated with
it(again not so important), but it also gives us the OS name and OS version, it
is running. Wow!!! It gives hackers who want to break into their server the
ultimate piece of information, which they require.
Well, these were the common ways of finding out more information
about a host in your quest to break into it. I will soon be updating this
manual, hope you enjoyed the first edition. Till the next update, goodbye.
COMING SOON: Finding out more Information about the remote host.
Exploiting the R Services (rlogin etc) or
Exploiting Trust Relationships
Exploiting Routers
More Fun with Remote Hosts
Ankit Fadia
ankit@bol.net.in [Yes, I answer all my mails ASAP]
The Hacking Truths Archive: http://hackingtruths.webprovider.com
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