The latest revelation about the National Security Agency's (NSA) expansive surveillance program isn't really a revelation at all. It comes from Germany's Der Spiegel magazine, which reports that smartphones powered by Apple's iOS, Google's Android, and Blackberry's operating systems are among the devices government spies exploit when they want to intercept a target's communications.

Buried in Monday's ho-hum report, however, is this intriguing nugget:

The NSA analysts are especially enthusiastic about the geolocation data stored in smartphones and many of their apps, data that enables them to determine a user's whereabouts at a given time. According to one presentation, it was even possible to track a person's whereabouts over extended periods of time, until Apple eliminated this "error" with version 4.3.3 of its mobile operating system and restricted the memory to seven days.

The lack of specifics in the article makes it hard identify the iOS bug, but it sure sounds like the one a pair of researchers reported in April 2011. It allowed anyone with physical access to an iPhone or iPad, or potentially a data backup of the device, to reconstruct a detailed account of the user's comings and goings, often down to the second, over an extended period of time. The geolocation data was stored in an easy-to-read file that was updated in real time, putting users at increased risk should their devices, computers, or backups ever fall into the hands of a hacker or government snoop who knew about the undocumented behavior.

In the weeks following the disclosure by researchers Alasdair Allan and Pete Warden, Apple defended the behavior, which was most likely intended to improve the performance of iPhones and iPads. Apple ultimately updated iOS to prevent it from storing such a detailed list of locations over such a long period of time. Version 4.3.3, according to Wikipedia, was released a month after the bug came to light. The changes included reducing the size of the "crowd-sourced location database," no longer backing it up to iTunes, and deleting it entirely when location services were turned off.

Is this the change that broke the hearts of NSA agents by preventing them from tracking the long-term movements of iPhone users? Probably. Researcher Warden confirmed to Ars that 4.3.3 was the release that closed the snooping hole he and Allan disclosed. But even if it's not, the geolocation caching behavior is a good example of the way even innocuous-sounding features designed to improve users' experiences can be used maliciously against them by adversaries. The Spiegel article goes on to say that NSA agents describe such attacks as exploiting the "carefree approach many users take to the device." One NSA document cited referred to the attitude as "nomophobia"—short for no mobile phobia—since the only thing agents perceived users fearing was the lack of connectivity.

After their discovery became public, Warden and Allan learned that forensic investigators had been exploiting the bug for years to dredge up the comings and goings of iPhone users involved in civil or criminal court cases.

"It's interesting to see the NSA was using it to snoop around, too," Warden said in a phone interview.