Early prediction of denial-of-service attacks

Daniel Keys Moran's long-awaited fourth instalment of his Tales of the Continuing Time having finally come out, I'm now, having read it, rereading the second book, The Long Run, written in 1989. During the course of this, I was astonished to come across the following passage:

Johnny Johnny submitted to the sentinel a request for access, watched the sentinel as it executed, considered the request and denied it. The sentinel was a small program, though well coded, with less than ten gigabytes of workspace memory assigned to it. Johnny Johnny fired another request, then another. The sentinel employed a primitive sort of ghosting, multitasking the two requests together. It slowed noticeably, and expanded slightly to claim more of the memory available to it.

Johnny Johnny ghosted himself a thousand thousand times.

And then each ghost started asking for entry to Level Three.

[...] The sentinel ballooned wildly, expanded to fill the maximum workspace allotted it. Johnny Johnny fired request after request at the sentinel even after it had reached peak load. The sentinel attempted to re-allocate memory internally, to shell out memory being used by the instruction stack and reassign that memory to the queued requests of a million ghosts.

Web angels appeared out of nowhere, tore into Johnny Johnny's ghosts. Johnny Johnny ignored the web angels, concentrating on the sentinel—

—which was faltering. The sentinel oscillated wildly, thrashing senselessly in its attempts to deal with the massive overload of data. Johnny Johnny kept up the stream of new requests, pushing now as the sentinel—

—crashed.

And there you have it: a description of a denial-of-service request, written a dozen years before such things became reality (at least according to Wikipedia). Another impressive prediction by DKM, to sit alongside that of Net addiction (which he called "datastarve").

Does anyone know of any earlier reference to denial-of-service attacks, whether in science fiction, academia, or reality?