"The word hack doesn't really have
69 different meanings", according to MIT hacker Phil Agre. "In
fact, hack has only one meaning, an
extremely subtle and profound one which defies articulation.
Which connotation is implied by a given use of the word depends
in similarly profound ways on the context. Similar remarks apply
to a couple of other hacker words, most notably random."
Hacking might be characterized as `an appropriate application
of ingenuity'. Whether the result is a quick-and-dirty patchwork
job or a carefully crafted work of art, you have to admire the
cleverness that went into it.
An important secondary meaning of hack is `a creative practical joke'. This kind of
hack is easier to explain to non-hackers than the programming
kind. Of course, some hacks have both natures; see the lexicon
entries for pseudo and kgbvax. But here are some examples of pure
practical jokes that illustrate the hacking spirit:
In 1961, students from Caltech (California Institute
of Technology, in Pasadena) hacked the Rose Bowl football game.
One student posed as a reporter and `interviewed' the director of
the University of Washington card stunts (such stunts involve
people in the stands who hold up colored cards to make pictures).
The reporter learned exactly how the stunts were operated, and
also that the director would be out to dinner later.
While the director was eating, the students (who called
themselves the `Fiendish Fourteen') picked a lock and stole a
blank direction sheet for the card stunts. They then had a
printer run off 2300 copies of the blank. The next day they
picked the lock again and stole the master plans for the stunts
-- large sheets of graph paper colored in with the stunt
pictures. Using these as a guide, they made new instructions for
three of the stunts on the duplicated blanks. Finally, they broke
in once more, replacing the stolen master plans and substituting
the stack of diddled instruction sheets for the original set.
The result was that three of the pictures were totally
different. Instead of `WASHINGTON', the word ``CALTECH' was
flashed. Another stunt showed the word `HUSKIES', the Washington
nickname, but spelled it backwards. And what was supposed to have
been a picture of a husky instead showed a beaver. (Both Caltech
and MIT use the beaver -- nature's engineer -- as a mascot.)
After the game, the Washington faculty athletic representative
said: "Some thought it ingenious; others were indignant." The
Washington student body president remarked: "No hard feelings,
but at the time it was unbelievable. We were amazed."
This is now considered a classic hack, particularly because
revising the direction sheets constituted a form of
programming.
Here is another classic hack:
On November 20, 1982, MIT hacked the Harvard-Yale
football game. Just after Harvard's second touchdown against
Yale, in the first quarter, a small black ball popped up out of
the ground at the 40-yard line, and grew bigger, and bigger, and
bigger. The letters `MIT' appeared all over the ball. As the
players and officials stood around gawking, the ball grew to six
feet in diameter and then burst with a bang and a cloud of white
smoke.
The "Boston Globe" later reported: "If you want to know the
truth, MIT won The Game."
The prank had taken weeks of careful planning by members of
MIT's Delta Kappa Epsilon fraternity. The device consisted of a
weather balloon, a hydraulic ram powered by Freon gas to lift it
out of the ground, and a vacuum-cleaner motor to inflate it. They
made eight separate expeditions to Harvard Stadium between 1 and
5 A.M., locating an unused 110-volt circuit in the
stadium and running buried wires from the stadium circuit to the
40-yard line, where they buried the balloon device. When the time
came to activate the device, two fraternity members had merely to
flip a circuit breaker and push a plug into an outlet.
This stunt had all the earmarks of a perfect hack: surprise,
publicity, the ingenious use of technology, safety, and
harmlessness. The use of manual control allowed the prank to be
timed so as not to disrupt the game (it was set off between
plays, so the outcome of the game would not be unduly affected).
The perpetrators had even thoughtfully attached a note to the
balloon explaining that the device was not dangerous and
contained no explosives.
Harvard president Derek Bok commented: "They have an awful lot
of clever people down there at MIT, and they did it again."
President Paul E. Gray of MIT said: "There is absolutely no truth
to the rumor that I had anything to do with it, but I wish there
were."
The hacks above are verifiable history; they can be proved to
have happened. Many other classic-hack stories from MIT and
elsewhere, though retold as history, have the characteristics of
what Jan Brunvand has called `urban folklore' (see FOAF). Perhaps the best known of these is the
legend of the infamous trolley-car hack, an alleged incident in
which engineering students are said to have welded a trolley car
to its tracks with thermite. Numerous versions of this have been
recorded from the 1940s to the present, most set at MIT but at
least one very detailed version set at CMU.
Brian Leibowitz has researched MIT hacks both real and
mythical extensively; the interested reader is referred to his
delightful pictorial compendium "The Journal of the Institute for
Hacks, Tomfoolery, and Pranks" (MIT Museum, 1990; ISBN
0-917027-03-5). The Institute has a World Wide Web page at http://hacks.mit.edu/Hacks/Gallery.html.
There is rumored to be a sequel entitled "Is This The Way To
Baker Street?". The Caltech Alumni Association has published two
similar books titled "Legends of Caltech" and "More Legends of
Caltech".
Finally, here is a story about one of the classic computer
hacks.
Back in the mid-1970s, several of the system support
staff at Motorola discovered a relatively simple way to crack
system security on the Xerox CP-V timesharing system. Through a
simple programming strategy, it was possible for a user program
to trick the system into running a portion of the program in
`master mode' (supervisor state), in which memory protection does
not apply. The program could then poke a large value into its
`privilege level' byte (normally write-protected) and could then
proceed to bypass all levels of security within the
file-management system, patch the system monitor, and do numerous
other interesting things. In short, the barn door was wide open.
Motorola quite properly reported this problem to Xerox via an
official `level 1 SIDR' (a bug report with an intended urgency of
`needs to be fixed yesterday'). Because the text of each SIDR was
entered into a database that could be viewed by quite a number of
people, Motorola followed the approved procedure: they simply
reported the problem as `Security SIDR', and attached all of the
necessary documentation, ways-to-reproduce, etc.
The CP-V people at Xerox sat on their thumbs; they either
didn't realize the severity of the problem, or didn't assign the
necessary operating-system-staff resources to develop and
distribute an official patch.
Months passed. The Motorola guys pestered their Xerox
field-support rep, to no avail. Finally they decided to take
direct action, to demonstrate to Xerox management just how easily
the system could be cracked and just how thoroughly the security
safeguards could be subverted.
They dug around in the operating-system listings and devised a
thoroughly devilish set of patches. These patches were then
incorporated into a pair of programs called `Robin Hood' and
`Friar Tuck'. Robin Hood and Friar Tuck were designed to run as
`ghost jobs' (daemons, in Unix terminology); they would use the
existing loophole to subvert system security, install the
necessary patches, and then keep an eye on one another's statuses
in order to keep the system operator (in effect, the superuser)
from aborting them.
One fine day, the system operator on the main CP-V software
development system in El Segundo was surprised by a number of
unusual phenomena. These included the following:
Tape drives would rewind and dismount their tapes in the
middle of a job.
Disk drives would seek back and forth so rapidly that they
would attempt to walk across the floor (see walking drives).
The card-punch output device would occasionally start up of
itself and punch a lace card.
These would usually jam in the punch.
The console would print snide and insulting messages from
Robin Hood to Friar Tuck, or vice versa.
The Xerox card reader had two output stackers; it could be
instructed to stack into A, stack into B, or stack into A (unless
a card was unreadable, in which case the bad card was placed into
stacker B). One of the patches installed by the ghosts added some
code to the card-reader driver... after reading a
card, it would flip over to the opposite stacker. As a result,
card decks would divide themselves in half when they were read,
leaving the operator to recollate them manually.
Naturally, the operator called in the operating-system
developers. They found the bandit ghost jobs running, and gunned them... and were once
again surprised. When Robin Hood was gunned, the following
sequence of events took place:
!X id1
id1: Friar Tuck... I am under attack! Pray save me!
id1: Off (aborted)
id2: Fear not, friend Robin! I shall rout the Sheriff
of Nottingham's men!
id1: Thank you, my good fellow!
Each ghost-job would detect the fact that the other had been
killed, and would start a new copy of the recently slain program
within a few milliseconds. The only way to kill both ghosts was
to kill them simultaneously (very difficult) or to deliberately
crash the system.
Finally, the system programmers did the latter -- only to find
that the bandits appeared once again when the system rebooted! It
turned out that these two programs had patched the boot-time OS
image (the kernel file, in Unix terms) and had added themselves
to the list of programs that were to be started at boot time
(this is similar to the way MS-DOS viruses propagate).
The Robin Hood and Friar Tuck ghosts were finally eradicated
when the system staff rebooted the system from a clean boot-tape
and reinstalled the monitor. Not long thereafter, Xerox released
a patch for this problem.
It is alleged that Xerox filed a complaint with Motorola's
management about the merry-prankster actions of the two employees
in question. It is not recorded that any serious disciplinary
action was taken against either of them.
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