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In fact, many ISPs use nothing more than networked PCs running
Linux!
As a result, all the computing, data storage, and sending,
receiving and forwarding of messages on the Internet is handled
by the millions of computers of many types and owned by countless
companies, educational institutions, governmental entities and
even individuals.
Each of these computers has an individual address which enables
it to be reached through the Internet if hooked up to a appropriate
communications link. This address may be represented in two ways:
as a name or a number.
The communications links of the Internet are also owned and
maintained in the same anarchic fashion as the hosts. Each owner
of an Internet host is responsible for finding and paying for
a communications link that will get that host tied in with at
least one other host. Communications links may be as simple
as a phone line, a wireless data link such as cellular digital
packet data, or as complicated as a high speed fiber optic link.
As long as the communications link can use TCP/IP or UUCP, it
can fit into the Internet.
Thus the net grows with no overall coordination. A new owner
of an Internet host need only get permission to tie into one
communications link to one other host. Alternatively, if the
provider of the communications link decides this host is, for
example, a haven for spammers, it can cut this “rogue site”
off of the Internet. The rogue site then must snooker some other
communications link into tying it into the Internet again.
The way most of these interconnected computers and communications
links work is through the common language of the TCP/IP protocol.
Basically, TCP/IP breaks any Internet communication into discrete
"packets." Each packet includes information on how
to rout it, error correction, and the addresses of the sender
and recipient. The idea is that if a packet is lost, the sender
will know it and resend the packet. Each packet is then launched
into the Internet. This network may automatically choose a route
from node to node for each packet using whatever is available
at the time, and reassembles the packets into the complete message
at the computer to which it was addressed.
These packets may follow tortuous routes. For example, one
packet may go from a node in Boston to Amsterdam and back to
the US for final destination in Houston, while another packet
from the same message might be routed through Tokyo and Athens,
and so on. Usually, however, the communications links are not
nearly so torturous. Communications links may include fiber optics,
phone lines and satellites.
The strength of this packet-switched network is that most
messages will automatically get through despite heavy message
traffic congestion and many communications links being out of
service. The disadvantage is that messages may simply disappear
within the system. It also may be difficult to reach desired
computers if too many communications links are unavailable at
the time.
However, all these wonderful features are also profoundly
hackable. The Internet is robust enough to survive -- so its
inventors claim -- even nuclear war. Yet it is also so weak that
with only a little bit of instruction, it is possible to learn
how to seriously spoof the system (forged email) or even temporarily
put out of commission other people's Internet host computers
(flood pinging, for example.)
On the other hand, the headers on the packets that carry hacking
commands will give away the account information from which a
hacker is operating. For this reason it is hard to hide perfectly
when on the Internet.
It is this tension between this power and robustness and weakness
and potential for confusion that makes the Internet a hacker
playground.
For example, HERE IS YOUR HACKER TIP YOU’VE BEEN WAITING
FOR THIS ISSUE:
ftp://ftp.secnet.com
This ftp site was posted on the BUGTRAQ list, which is dedicated
to discussion of Unix security holes. Moderator is Aleph One,
who is a genuine Uberhacker. If you want to subscribe to the
BUGTRAQ, email LISTSERV@netspace.org with message “subscribe
BUGTRAQ.”
Now, back to Internet basics.
History of Internet
As mentioned above, the Internet was born as a US Advanced
Research Projects Agency (ARPA) effort in 1969. Its inventors
called it ARPANET. But because of its value in scientific research,
the US National Science Foundation (NSF) took it over in 1983.
But over the years since then it gradually evolved away from
any single source of control. In April 1995 NSF cut the last
apron strings. Now the Internet is run by no one. It just happens
and grows out of the efforts of those who play with it and struggle
with the software and hardware.
Nothing at all like this has ever happened before. We now
have a computer system with a life of its own. We, as hackers,
form a big part of the mutation engine that keeps the Internet
evolving and growing stronger. We also form a big part of the
immune system of this exotic creature.
The original idea of ARPANET was to design a computer and
communications network that would eventually become so redundant,
so robust, and so able to operate without centralized control,
that it could even survive nuclear war. What also happened was
that ARPANET evolved into a being that has survived the end of
government funding without even a blip in its growth. Thus its
anarchic offspring, the Internet, has succeeded beyond the wildest
dreams of its original architects.
The Internet has grown explosively, with no end in sight.
At its inception as ARPANET it held only 4 hosts. A quarter of
a century later, in 1984, it contained only 1000 hosts. But over
the next 5 years this number grew tenfold to 10,000 (1989). Over
the following 4 years it grew another tenfold to 1 million (1993).
Two years later, at the end of 1995, the Internet was estimated
to have at least 6 million host computers. There are probably
over 10 million now. There appears to be no end in sight yet
to the incredible growth of this mutant child of ARPANET.
In fact, one concern raised by the exponential growth in the
Internet is that demand may eventually far outrace capacity.
Because now no entity owns or controls the Internet, if the capacity
of the communications links among nodes is too small, and it
were to become seriously bogged down, it might be difficult to
fix the problem.
For example, in 1988, Robert Morris, Jr. unleashed a "virus"-type
program on the Internet commonly known as the “Morris Worm.”
This virus would make copies of itself on whatever computer it
was on and then send copies over communications links to other
Internet hosts. (It used a bug in sendmail that allowed access
to root, allowing the virus to act as the superuser).
Quickly the exponential spread of this virus made the Internet
collapse from the communications traffic and disk space it tied
up.
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