Apple Inc. denied Wednesday that iPhones store a record of their users' movements for up to a year and blamed privacy concerns partly on a misunderstanding.

A data file publicized by security researchers last week doesn't store users' locations, but a list of Wi-Fi hotspots and cell towers in their general area, the company said. It promised software fixes to address concerns over that file.

The data, downloaded from Apple, help the phone figure out its location without having to listen for faint signals from GPS satellites. That means navigation applications can present the phone's location faster and more accurately, Apple said.

Software error blamed

Apple said the data are stored for up to a year because of a software error. The company said there's no need to store data for more than seven days, and a software update in the next few weeks will limit the amount of data in that file.

The iPhone will also stop backing up the file to the user's computer, a practice that raised some concerns. Computers are much more vulnerable to remote hacking attempts than are phones.

A third planned fix is to stop downloading the data to phones that have all "location services" turned off, Apple said, and to encrypt the file on those where it's on.

"Users are confused, partly because creators of this new technology (including Apple) have not provided enough education about these issues to date," Apple said in its statement.

Wednesday's statement was Apple's first comprehensive response to the most recent allegations. Apple had revealed the nature of the location file in a letter to Congress last summer after an earlier round of questions about its location-tracking practices.

The file drew new attention last week, after a report from researchers Alasdair Allan and Pete Warden at a technology conference in Santa Clara, Calif.

As demonstrated by location-analysis software released by Allan and Warden, the lists of Wi-Fi hotspots and cell towers generated by iPhones can be used to construct a general record of users' movements.

But a snoop needs access to the victim's phone or PC, both of which usually store lots of other personal information. Phones contain texts, emails and lists of phone calls. PCs contain such information as tax returns, logs of websites visited and passwords.

In an email, Warden said it was good to have an explanation for the existence of the file. He agreed that it doesn't contain precise location information.

"By pulling down information about nearby towers, the log can reveal where you are at a neighborhood level," he said, adding that he's relieved that Apple is applying software fixes.

Edward Markey, a Democratic congressman from Massachusetts, questioned whether the practice was legal under a federal law governing the use of location information for commercial purposes, if consumers weren't properly informed.

Data anonymous: Apple

In Wednesday's statement, Apple reiterated that while iPhones regularly transmit their location to Apple, they do so only anonymously, and the company isn't able to track users. It can also transmit a user's location to companies that buy ads through Apple's iAds advertising system, but only if the user approves giving the current location to a particular ad.

Apple shares fell $1.70 US, or 0.5 per cent, to $348.72 in morning trading Wednesday.