"Burning" a communication device has been a mainstay of those interested in privacy, from the IMF (you know, from Mission: Impossible) to the corner boys on The Wire, and everyone in between. Those of us who aren’t superhuman secret agents or clever criminals may have a much more mundane reason for wanting to create a temporary phone number that routes to your actual number. Someone creating an online ad, a telemarketer trying to appear local so you'll pick up, or an uncertain party in a blind date could all use a throwaway number. Enter Burner, an iPhone app that debuted on Wednesday.

Sure, these days, you can use Google Voice, SkypeIn, or a number of any other services, but what’s nice about Burner is that you can do it from your own iPhone (an Android version is coming soon) in an instant. All I had to give Burner was my phone number. The company doesn’t even know my name or have my e-mail address. And yes, as expected, some people are already using it to create "casual encounters"-style personal ads (possibly NSFW).

I created my own Burner number in about 20 seconds. It defaults to your actual area code (in my case, 510), but you can choose a different one if you like. The app costs $2 and comes with a single temporary phone number and enough credits for a 20-minute phone call, which I burned through (excuse the pun) while on the phone with Greg Cohn, the co-founder and CEO of Ad Hoc Labs, the app’s parent company. Users can buy more numbers or add credit if necessary, or disconnect themselves from the temporary number by "burning" it in the app.

"There is a broader thesis that we have around identity and privacy," Cohn told me. "We definitely think that communications, and telephony specifically, have been left behind by the wave of social innovation that’s been happening. The network should be smarter, it should be more socially aware and more privacy-aware."

Cohn, the former director of business development at Yahoo, outlined a number of legitimate scenarios in which the company anticipates the app might work. A publicist may only want to give out a number for a weekend, or a week, while coordinating a local event. Or, a political campaign may want to issue temporary numbers for phone banks.

"The person who has burned the number is not reachable on that number," Cohn added. "We think of it as a temporary social network. You’re just giving them a path to you that works for right now. When you burn that number, that path dissolves. As well, we wipe the history from your phone."



Burn, baby, burn

Of course, the real question remains, how private is Burner, really? The short answer: it’s probably not a good idea to use Burner for things that are dodgy, highly confidential, and/or mission-critical private. This is not, Cohn told me, an end-to-end encrypted way to make phone calls.

First off, the company says it "expressly prohibits" using the app for "unlawful, criminal, or otherwise objectionable activities."

"We will only provide non-public information in response to law enforcement requests when they are made subject to US laws and via valid legal process, for example, a valid court order, or search warrant," the terms of service also states. "It is our policy to notify users of law enforcement requests unless prohibited from doing so by statute or valid court order."

Beyond that, though, there are more practical matters of confidentiality and secrecy, once a number has been "burned."

"As you can imagine, there's still records from your dialer and your carrier," Cohn added. "We don’t hold your phone up to a beam, like from Men in Black, and erase every piece of data from it. We can only read the records inside the app. We do retain backups and we do retain records of association between burner phone numbers for a period of time. Some of that information would be available should there be a law enforcement inquiry about it."

The app’s privacy policy, which is posted on the company website, puts it this way: "Backup copies of this data are not immediately deleted, however, and some aspects of user history are maintained for longer periods of time so that we can reconcile our records and manage our business."

Cohn declined to say precisely how long the company’s backups last.

In an e-mail, though, he did clarify that the app does not ask for any "explicit location data," such as a GPS location, but that it does log IP addresses.

"While we couldn't ourselves turn this log of IP addresses into a history of user locations at the level of cell-tower granularity, I'm not prepared to say that others couldn't if accessing our data (by subpoena, for example)," Cohn noted.

Legal experts like Hanni Fakhoury, a staff attorney at the Electronic Frontier Foundation, call Burner a "good start" as a "casual tool" for privacy.

"As far as I understand the app, the ‘burner’ number is routed to your personal cell phone number, and as long as [that] number is operating, there may be a way for law enforcement to eventually trace the ‘burned’ number back to the original cell phone," Fakhoury wrote in an e-mail to Ars.