The Smoking Gnu
In the bad old days of the clacks, many workers in the lonely outposts collapsed under the stress of long shifts of intense concentration in the swaying towers. It was said that some who came down from the towers were men1 whom ordinary madmen called mad. Their madness took various forms, however; some dangerous to themselves, some to society, some only to very specific and quite rational targets.
Two of these, known as "Mad Al" Winton and "Sane Alex" Carlton, turned their skill and experience against the Grand Trunk Semaphore Company. They called themselves crackers and devised ways of introducing damaging messages into the system. The two were an Odd Couple, Al the free spirit surrounded by clutter, and Alex the anal-compulsive, but "Mad" Al was not obviously madder than "Sane" Alex; indeed, Al tended to be the leader and spokesman. Acquiring an expelled (through the chimney) student Alchemist called "Undecided Adrian" Emery (who was no madder than the average Alchemist), they formed the Smoking Gnu. Al and Alex devised code and stratagems for "cracking" the system, while Adrian created new hardware to assist them as well as to improve a future clacks technology.
They created a packet of code2 called the Woodpecker which would have destroyed many of the chain of towers, but Moist von Lipwig persuaded them to send a different message: a "neutron bomb" which would destroy the corrupt company but leave the towers standing.
1They were all men, in the early days. Women3 would follow, but they missed the worst.
3In fact, they tended to be boys and girls.
Those familiar with GNU will gneed gno elaboration on the Ourobourosian joke around it, others, even less.
This may be a reference to The Smoking Gun and also a reference to the "Smoking Gun" tape involved in the Watergate scandal, or the Lone Gunmen from Chris Cater's X-files, who could also be described in similar terms as the the members of the Smoking Gnu (Two were "hackers" and the third an ex employee of the FCC).
In addition, the Woodpecker itself likely refers to the Russian Woodpecker.