Under the Patriot Act, the US government can demand information from companies and ask them to keep the order secret, but there's a clever legal feint that can sidestep this: a so-called "warrant canary." Now it appears Apple may have sent up the signal.

In its first transparency report, where it documents legal requests, Apple included this footnote: "Apple has never received an order under Section 215 of the USA Patriot Act. We would expect to challenge such an order if served on us." Many believed this to be a canary — a line that would disappear if and when Apple received a Patriot Act order, silently (and, although it hasn't been tested in court, perhaps legally) informing close readers. As flagged by GigaOm, Apple's last two transparency reports, which include the last half of 2013 and first half of 2014, dropped the canary — or at least changed the language in it — suggesting the company may have been ordered to hand over records under the Patriot Act. Now the report only reads this: "To date, Apple has not received any orders for bulk data."

Several tech companies recently fought for the right to begin disclosing national security requests, but won only the option to disclose them in certain numbers. If less than 1,000 requests have been sent, for example, the company may only disclose that the number of requests was between zero and 999. Hence the need for the canary: Apple reports in "bands" of 250, and the "zero to 250" number didn't change between transparency reports, suggesting the company may have received at least one.

Meanwhile, other companies are in a similar spot: Facebook reports "zero to 999" national security requests, as does Google.

Update: As pointed out on Twitter, although the language has changed to not specifically mention the Patriot Act, Apple still includes one line in their report: "To date, Apple has not received any orders for bulk data." This article has also been updated to reflect that Apple reports national security requests in bands of 250.