CALLBACK UNITS:
Callback units are a good security device, But with most phone systems,
it is quite possible for the hacker to use the following steps to get
around a callback unit that uses the same phone line for both incomming
and out going calls:First, he calls he callback unit and enters any
authorized ID code (this is not hard to get,as you'll see in a moment).
After he enters this ID, the hacker holds the phone line open - he does
not hang up. When the callback unit picks up the phone to call the user back,
the hacker is there, waiting to meet it.
The ID code as I said, is simple for a hacker to obtain, because these
codes are not meant to be security precautions.The callback unit itself
provides security by keeping incomming calls from reaching the computer.
The ID codes are no more private than most telephone numbers. Some callback
units refer to the codes as "location identification numbers," and some
locations are used by several different people,so their IDs are fairly
well known.I've been told that, in some cases,callback ubits also have
certain simple codes that are always defined by default. Once the hacker
has entered an ID code and the callback unit has picked up the phone to
re-call him,the hacker may or may not decide to provide a dial tone to
allow the unit to "think" it is calling the correct number. In any event,
the hacker will then turn on his computer, connect with the system - and
away he goes.If the however, the hacker has trouble holding the line with
method,he has an option: the intercept.
The Intercept:
Holding the line will only work with callback units that use the same
phone lines to call in and to call out.Some callback units use different
incoming and outgoing lines, numbers 555-3820 through 555-3830 are dedicated
to users' incoming calls, and lines 555-2020 through 555-2030 are dedicated
to the computers outgoing calls.The only thing a hacker needs in order to
get through to these systems is a computer and a little time - he doesn't
even need an ID code. First,the hacker calls any one of the outgoing phone
lines, which, of course, will not answer.Sooner or later, though, while the
hacker has his computer waiting there, listening to the ring, an authorized
user will call one of the incomming lines and request to be called back.
It will usually be less than an hours wait, but the hacker's computer
is perfectly capable of waiting for days, if need be.
The callback unit will take the code of the authorized user, hang up,
verify the code, and pick up the phone line to call back.If the unit
tries to call out on the line the hacker has dialed, the hacker has his
computer play a tone that sounds just like a dial tone.The computer will
then dial the number given that matches up with the user's authorized ID.
After that,the hacker can just connect his computer as he would in any
other case.If he is really serious,he will even decode the touch tones
that the mainframe dialed,figure out the phone number of the user the
system was calling, call the person, and make a few strange noises that
sound as though the computer called back but didnt work for some reason.
2) TRAPDOORS AS A POSSIBLILITY
I haven't heard of this happening, but i think it is possible that a
callback modem could have a trapdoor built into it.Callback modems are
run by software, which is written by programmers.An unscrupulous programmer
could find it very easy to slip in an unpublicized routine, such as,
"if code =*43*, then show all valid codes and phone numbers." And such a
routine, of course, would leave security wide open to anyone who found the
trapdoor.The obvious protection here, assuming the situation ever arises,
is simply an ethical manufactorer that checks its software thoroughly before
releasing it.
A trapdoor is a set of special instructions embedded in the large
program that is the operating system of a computer.A permanent,
hopefully secret "doorway", these special instructions enabe anyone who
knows about them to bypass normal security procedures and to gain access to
the computer's files.Although they may sound sinister, trapdoors were not
invented by hackers, although existing ones are certainly used by hackers
who find out about them.
3) THE DECOY
One of the more sophisticated hacking tools is known as the decoy, and it
comes in three versions.The first version requires that the hacker have an
account on the system in question. As in my case,the hacker has a
low-security account,and he tries this method to get higher-security
account.He will first use his low-security account to write a program that
will emulate the log-on procedures of the systems in questions.
This program will do the following:
*- Clear the terminal screen and place text on it that makes everything
look as if the system is in charge.
*- Prompt for, and allow the user to enter, both an account name and a password.
*- Save that information in a place the hacker can access.
*- Tell the use the account/password entries are not acceptable.
*- turn control of the terminal back over to the system.
The user will now assume that the account name or password was mistyped
and will try again...this time (scince the real operating system is in
control) with more success.You can see a diagram of the way these steps are
accomplished
___________________
| Clear Terminal |
| screen |
|____________________|
||
_________||_________
| Print Compuserve |
| Computer |
|_____ Network ______|
||
_________||_________
| Print "ENTER |
| PASSWORD" |______
|____________________| |
|| |
_________||_________ |
| PASSWORD ENTERED? |__NO__|
|____________________|
||_YES
_________||_________
| SAVE PASSWORD |
| INFORMATION |
|____________________|
||
_________||_________
| PRINT "LOGIN |
| INCORRECT |
|____________________|
||
_________||_________
| LOG OFF/RETURN |
| CONTROL TO |
| OPERATING SYSTEM |
|____________________|
4) CALL FORWARDING
Many people use call forwarding by special arrangement with the phone
company.When a customer requests call forwarding, the phone company uses
its computer to forward all the customers incomeing calls to another
number. Lets say, for example, that you want calls that come to your office
phone to be forwarded to your home phone: A call from you to the phone
company,some special settings in the phone companys computer, and all
calls to your office will ring at your home instead.This little bit of help
from the phone company is another tool used by hackers. Lets say you thought
that the computer you were hacking into was being watched-because the
sysop might have seen you and called the fed's and your sort of bugged by
this nagging feeling that they will trace the next hacker that calls,
just call the phone company and ask for call forwarding, pick a number,
(ANY NUMBER) out of the phone book and have your calls forwarded to that
number,Hea,Hea, the number you picked is the one that will be traced to,
not yours, so you could be hacking away,they think that they have traced you,
but actually the number you had your calls forwarded too. they enter chat mode
and say (YOUR BUSTED!!!!, WE'VE TRACED YOUR PHONE NUMER THE FEDS ARE ON THE
WAY!!), You could reply (Hea, SURE YA DID! I'D LIKE TO SEE YA TRY AND GET ME!
GO AHEAD!) ,that wont seem very important to them at the time, but it will
sure piss them off when they bust the wrong guy!
5) RAPID FIRE
Memory-location manipulation can be helpful, but there is another, more
powerful,possibility, in some cases: the Rapid-fire method.To understand how
this methos works, you have to know something about the way operationg
systems work.When a user enters a command, the operating system first places
the command in a holding area, a buffer, where it will sit for a few
millionths of a second.The system looks at the command and say's "Does this
person really have authorization to do this, or not?" Then, the command
sits there a few thousandths of a second while the system runs off to
check the user's authorization.When the system comes back to the command,
it will have one of two possible answers: "OK, GO AHEAD," or "SORRY,
GET PERMISSION FIRST."
Once you are on a system that handles things this way, you can