From Wikipedia, a kōan is a story, dialogue, question, or statement, which is used in Zen-practice to provoke the "great doubt", and test a student's progress in Zen practice.
A cryptography mailing list had the following during the time of when the Heartbleed Bug reared it's ugly head. It is a pity, longer kōan regarding how one should approach development practices, and is a nod towards current code sharing "in the large".
A novice asked of master Bawan: "Say something about the Heartbleed Bug."
Said Bawan: "Chiuyin, the Governor's treasurer, is blind as an earthworm. A thief may give him a coin of tin, claim that it is silver and receive change. When the treasury is empty, which man is the villain? Speak right and I will spare you all blows for one week. Speak wrong and my staff will fly!"
The novice thought: if I say the thief, Bawan will surely strike me, for it is the treasurer who doles out the coins. But if I say the treasurer he will also strike me, for it is the thief who takes advantage of the situation.
When the pause grew too long, Bawan raised his staff high. Suddenly enlightened, the novice cried out: "The Governor! For who else made this blind man his treasurer?"
Bawan lowered his staff. "And who is the Governor?"
Said the novice: "All who might have cried out 'this man is blind!' but failed to notice, or even to examine him."
Bawan nodded. "This is the first lesson. Too easily we praise Open Source, saying smugly to each other, 'under ten thousand eyeballs, every bug is laid bare'. Yet when the ten thousand avert their gaze, they are no more useful than the blind man. And now that I have spared you all blows for one week, stand at ease and tell me: what is the second lesson?"
Said the novice: "Surely, I have no idea."
Bawan promptly struck the novice's skull with his staff. The boy fell to the floor, unconscious.
As he stepped over the prone body, Bawan remarked: "Code as if everyone is the thief."
This and more can be found at The Codeless Code.
Other sites with kōans:
Added 2014/07/08: Vim Koans