ARPANET Hopping: America's Newest Pastime (June, 1984)
------------------------------------------------------

What is ARPANET?

ARPANET (Advanced Research Projects Agency Network) has been around since the
1960s. Its intentions were to link many computers together in order to share
resources. The various research projects on ARPANET involve both major
universities and the United States military (the two are closer than either
would care to admit).

Up until last year, ARPANET was one big happy family of military and university
computers. Then, in view of War Games, etc., it was decided that perhaps the
military would be better off on their own separate network. And so, MILNET was
established.

This proved to be very convenient for hackers, since they now knew where all of
the military computers were all it took was access to MILNET in order to play
with them.

Since ARPANET can communicate with MILNET and vice versa, all kinds of
interesting possibilities exist. Elaborate routing makes it easy for a hacker
to cover his trail, in much the same way that a phreak routes calls through
three different long distance companies to protect his/her identity.

Where can dialups to ARPANET be found? All over the place. For one thing, many
numbers are in circulation among hackers. For another, they're not considered
all that much of a secret, since the numbers by themselves don't allow you to
log on.

If you know of a major university computer, there's a chance that it's already
hooked into the ARPANET. If this is the case, HELP files will be readily
available on that system to explain how to access the network.

The network itself is an entire world waiting to be explored. Ironically, many
sensitive computers that are "not accessible by phone lines" are accessible by
ARPANET! There are a lot of lessons that still must be learned, it seems.

So Simple a Child Could Do It

Moving around ARPANET is very easy as almost any hacker that has used it will
attest to. It was designed upon the principle that people on one system should
have easy access to other systems. "Easy" is the key word here. If a direct
ARPANET dialup is being used, there shouldn't be any problem. If a MILNET
dialup is being used, you will need a TACID, which is a private authorization
code.

The word ARPANET is used to denote all networks. There are many networks (see
2600, May 1984), but all can be accessed as one through "gateways," which are
basically windows into other networks.

How It Works

There are two basic commands that can be used on the ARPANET: "@o" and "@c."
"@o" opens a connection with a host. (For example, @o 26.0.0.1 will connect you
with a host hooked to ARPANET-indicated by the 26.) Finding addresses is really
the only hard part. At one time, a few systems had a HOST command that would
give you a complete listing of hosts, and their addresses. In fact, this
command is still on many systems but what was unique here was the fact that you
could run the program without logging in!! Apparently, they got wise to
hackers, and fixed HOST so that it only works from logged in accounts.

After typing "@o," the network will respond with "Open" or, if the attempt was
less than successful, a self-explanatory error message such as "Bad" or
"Destination host dead." When you get the "Open" message, that means you are now
connected to the host computer and you can do whatever you want, like log in,
read help files, etc. Communication with the network is not cut off, however.
The network is always there, waiting to be spoken to. Commands to the network
must begin with "@." For example, type "@c" when you want to close the
connection with whatever computer you hooked into. This will probably take a
moment or two, since the network has to close up a few things before it can
transfer control back to you. (Incidentally, if you need to send a command to
the remote host that contains "@" in it simply type an extra "@" next to the
first one and ARPANET will ignore it.)

Some Safety Tips and Interesting Programs

If you can dial up to a host that is connected to ARPANET, and you have an
account on it, this is ideal. There is a good chance that the host will support
a terminal simulation program, that when supplied the hostname that you wish to
communicate with, will connect you to it through ARPANET. It will then seem as
if you're on a terminal connected to that remote host. To close the connection,
you will have to read the documentation on the host that you dialed up to,
since it changes from system to system. Naturally, using a local dialup to
access a host instead of going through a MILNET or ARPANET dialup is much
"safer," since you are not accessing ARPANET directly.

Another feature of ARPANET is the FINGER command available on most TOPS-20
systems, and many other types as well. The FINGER command will provide you with
a listing of people currently logged into the system, with some information on
them, such as their full name, where their terminal is located, and what their
account is known as. You will also show up on a FINGER, and it will show
whether you re on a remote host or not. FINGER followed by a valid account on
that system will give you some very detailed info on that person. One other
very nice feature of FINGER is that you can supply a remote hostname, and get a
listing of people on another host, without connecting to it!! (For instance,
FINGER @SRI-NIC will give you a listing of people logged onto the Network Info
Center.) Another program that gives details on users (though not all that much)
is SYSTAT. Both can, in many cases, be run without logging in, and many HELP
files are also accessible without logging in. Certain HELP files give
information on login formats or list dialup numbers.

If you have an account on a system, the chances are quite good that that system
will support FTP, which is short for File Transfer Protocol. This allows you to
take files from one system, and copy them to the system that you re on. The one
problem here is that you will need a valid account to use on the system you
wish to take the files from. Most (if not all) TOPS-20 systems support file
transfers, and consequently have an account set aside for that purpose. The
account is called "ANONYMOUS" and it works with any password. Some other hosts
use the account "ANONYMOUS" as well, but they are by no means consistent. The
way file transfers work is through an FTP on the system that you re presently
on. This program communicates through ARPANET with the host you want to take
files from. On the remote host, there will be a program running that will take
requests from other hosts, and transmit files through the network to them. You
can do more than take files, though. You can transmit files from the host you
are on to the remote host, or delete or rename files on the remote host, or get
a directory of an account on the remote host. It's very handy to get a file
from SRI-NIC, which contains all network base addresses, addresses of gateways
(ways of getting from one network to another), and addresses of all hosts on
all networks.

And, of course, there s the ARPANET mail system, which allows you to
communicate with any ARPANET user. It works in a similar fashion to FTP and
FINGER as far as roaming the network to find a matching username or host ID. It
is still said that there is a very active hacker community living in ARPANET
mailboxes and it hardly seems surprising when considering how fast and
efficiently this mail system works.

The Future

Since ARPANET was designed to be, and is still being, used by people who are
not very familiar with computers, it will always be easy to use ARPANET, and
"hop" about it. It's very unlikely that they will change it in any way, since it
is, for the most part, pretty good at keeping hackers away from things that
they're not supposed to be looking at.

Maybe...