There's some more stuff about it on Jordan's wikipedia page.
https://en.wikipedia.org/wiki/Jordan_Hubbard#rwall_incident

And Risks Digest: http://catless.ncl.ac.uk/Risks/4.73.html#subj10.1

I was one of the 743 people who received his rwall and immediately send him a message (which I've since lost) flaming about the evils of Sun RPC (and promising a longer flame). I saved his reply and some old email about it from the hackers_guild and tcp-ip mailing lists.

IIRC, the flame probably would have touched on the fact that among Sun RPC services, rcp.rwalld was hardly the worst offender: Sun's NFS rpc.mountd demon trusted the client's word on what its hostname is (it was passed from client to server as a parameter to the mount RPC call -- the server didn't check the ip address!), in order to authenticate the client's permission to mount a directory!

That's right, you actually could mount any NFS directory by going "hostname <hostname known to be in server's /etc/exports> ; mount server:/directory /mnt ; hostname <previous host name>". And you could usually use the equivalent of "tftp server:/etc/exports /tmp/server_exports" to discover a trusted hostname to use, because Suns were set up like that by default, out of the box!

Date: Tue, 31 Mar 87 12:02:53 PST
From: jkh%violet.Berkeley.EDU@berkeley.edu (Jordan K. Hubbard)
To: don@tumtum.cs.umd.edu
Subject: re: flame flame flame

Thanks, you were nicer than most.. Here's the stock letter I've been
sending back to people:

Thank you, thank you..

Now if I can only figure out why a lowly machine in a basement somewhere
can send broadcast messages to the entire world. Doesn't seem right
somehow.

Yours for an annoying network.

Jordan

P.S. I was actually experimenting to see exactly now bad a crock RPC was.
I'm beginning to get an idea. I look forward to your flame.

Jordan

----

Jordan's rwall scribbled all over Dennis Perry's Interleaf windows (who Jordan incorrectly referred to as the Inspector General of the ARPAnet in the Pentagon, and who was "absolutely livid" and threatened to cut off UCB's ARPANET access). Things were pretty wide open back then, and Jordan's "little incident" really stirred up a hornet's nest!

There were some interesting followups from heavy duty dudes like Milo Medin and Dennis Perry on the h_g/tcp-ip mailing lists:

From: Milo S. Medin <medin@orion.arpa>

Actually, Dennis Perry is the head of DARPA/IPTO, not a pencil pusher
in the IG's office. IPTO is the part of DARPA that deals with all
CS issues (including funding for ARPANET, BSD, MACH, SDINET, etc...).
Calling him part of the IG's office on the TCP/IP list probably didn't
win you any favors. Coincidentally I was at a meeting at the Pentagon
last Thursday that Dennis was at, along with Mike Corrigan (the man
at DoD/OSD responsible for all of DDN), and a couple other such types
discussing Internet management issues, when your little incident
came up. Dennis was absolutely livid, and I recall him saying something
about shutting off UCB's PSN ports if this happened again. There were
also reports about the DCA management types really putting on the heat
about turning on Mailbridge filtering now and not after the buttergates
are deployed. I don't know if Mike St. Johns and company can hold them
off much longer. Sigh... Mike Corrigan mentioned that this was the sort
of thing that gets networks shut off. You really pissed off the wrong
people with this move!

Dennis also called up some VP at SUN and demanded this hole
be patched in the next release. People generally pay attention
to such people.

From: Jordan K. Hubbard <jkh@violet.berkeley.edu>

Well, I hope Sun patches the holes, Milo. I'm sorry that certain people chose
to react as strongly as they did in our esteemed government offices, but
I am glad that it raised enough fuss to possibly get the problem fixed. No
data was destroyed, lost, or infiltrated, but some people got a whack on the
side of the head for leaving the back door open. I'm not sure I can say that
I'm all that sorry that this happened. rwall is certainly going to change on
my machines, I can only hope that people concerned about being rwall'd over
the net will tighten up their RPC. Those that don't care, should at least be
aware of it.

From: Dennis G. Perry <PERRY@vax.darpa.mil>

Jordan, you are right in your assumptions that people will get annoyed
that what happened was allowed to happen.

By the way, I am the program manager of the Arpanet in the Information
Science and Technology Office of DARPA, located in Roslin (Arlington), not
the Pentagon.

I would like suggestions as to what you, or anyone else, think should be
done to prevent such occurances in the furture. There are many drastic
choices one could make. Is there a reasonable one? Perhaps some one
from Sun could volunteer what there action will be in light of this
revelation. I certainly hope that the community can come up with a good
solution, because I know that when the problem gets solved from the top
the solutions will reflect their concerns.

Think about this situation and I think you will all agree that this is
a serious problem that could cripple the Arpanet and anyother net that
lets things like this happen without control.

dennis
———

From: Jordan K. Hubbard <jkh@violet.berkeley.edu>

Dennis,

Sorry about the mixup on your location and position within DARPA. I got
the news of your call to Richard Olson second hand, and I guess details
got muddled along the way. I think the best solution to this problem (and
other problems of this nature) is to tighten up the receiving ends. Assuming
that the network is basically hostile seems safer than assuming that it's
benign when deciding which services to offer.

I don't know what Sun has in mind for Secure RPC, or whether they will move
the release date for 4.0 (which presumably incorporates these features)
closer, but I will be changing rwalld here at Berkeley to use a new YP
database containing a list of "trusted" hosts. If it's possible to change
RPC itself, without massive performance degradation, I may do that as well.

My primary concern is that people understand where and why unix/network
security holes exist. I've gotten a few messages from people saying that
they would consider it a bug if rwall didn't perform in this manner, and
that hampering their ability to communicate with the rest of the network
would be against the spirit of all it stands for. There is, of course, the
opposite camp which feels that IMP's should only forward packets from hosts
registered with the NIC. I think that either point of view has its pros and
cons, but that it should be up to the users to make a choice. If they wish
to expose themselves to potential annoyance in exchange for being able to,
uh, communicate more freely, then so be it. If the opposite is true, then
they can take appropriate action. At least an informed choice will have been
made.

Yours for a secure, but usable, network.

From: Dennis G. Perry <PERRY@vax.darpa.mil>

Jordan, thanks for the note. I agree that we should discover and FIX holes
found in the system. But at the same time, we don't want to have to
shut the thing down until such a fix can be made. Misuse of the system
get us all in a lot of trouble. The Arpanet has succeeded because of
the self policing community. If this type of potential for disruption
gets used by very many people, I guarentee that we all will not like the
solution or fix proposed.

dennis
———