The editorial, titled "WikiLeaks, a Post Postscript," was purportedly published over the weekend by the Times and in every way appears to be the real thing from Keller, who until last September was the paper's executive editor.
The article appeared on a web page built to replicate the Times' popular website, right down to perfectly working links to the rest of the site.
It was so realistic that none other than the newspaper's technology editor Nick Bilton posted the link on his Twitter account, calling the apparent defense of Julian Assange's controversial organization an "important piece."
"THERE IS A FAKE OP-ED GOING AROUND UNDER MY NAME, ABOUT WIKILEAKS. EMPHASIS ON 'FAKE.' AS IN, NOT MINE," Keller, now a writer on the paper, tweeted to set the record straight.
Bilton followed up, tweeting: "I just deleted a tweet sent late last night that was from a fake NYT Bill Keller account."
One of the few clues to the forgery was the web address of http://www.opinion-nytimes.com/2012/07/29/opinion/keller-a-post-postscript.html,since the real website's URL begins with www.nytimes.com.
There was no immediate word on the identity of the pranksters, though the global hacking movement Anonymous has notched up high-profile hits on American institutions over the last year.
The New York Times is certainly no stranger to WikiLeaks: the US daily has been one of the principal outlets for Assange's mass dumping of hitherto secret government information from around the world.