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AirDrop is a feature that allows Apple devices to securely and conveniently transfer files, photos, and more between each other wirelessly. Users can share items with their own devices, friends, family, or even strangers. The convenience and ease of use, however, may be undermined by a newly discovered security flaw.

airdrop-logo.jpg

Researchers at TU Darmstadt have discovered that the process which AirDrop uses to find and verify someone is a contact on a receiver's phone can expose private information. AirDrop includes three modes; Receiving Off, Contacts Only, Everyone. The default setting is Contacts Only, which means only people within your address book can AirDrop photos, files, and more to your device.

The researchers discovered that the mutual authentication mechanism that confirms both the receiver and sender are on each other's address book could be used to expose private information. The researchers claim that a stranger can use the mechanism and its process within the range of an iOS or macOS device with the share panel open to obtain private information. As the researchers explain:
As an attacker, it is possible to learn the phone numbers and email addresses of AirDrop users – even as a complete stranger. All they require is a Wi-Fi-capable device and physical proximity to a target that initiates the discovery process by opening the sharing pane on an iOS or macOS device.

The discovered problems are rooted in Apple's use of hash functions for "obfuscating" the exchanged phone numbers and email addresses during the discovery process. However, researchers from TU Darmstadt already showed that hashing fails to provide privacy-preserving contact discovery as so-called hash values can be quickly reversed using simple techniques such as brute-force attacks.

To determine whether the other party is a contact, AirDrop uses a mutual authentication mechanism that compares a user's phone number and email address with entries in the other user's address book.
According to the researchers, Apple was informed of the flaw in May of 2019, and despite several software updates since then, the flaw remains.

Article Link: Researchers Discover AirDrop Security Flaw That Could Expose Personal Data to Strangers
 
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dannyyankou

macrumors G4
Mar 2, 2012
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According to the researchers, Apple was informed of the flaw in May of 2019, and despite several software updates since then, the flaw remains. We've reached out to Apple for comment and will update this article if we hear back.
I’m sure now that they made this public, Apple will move with more urgency. Apple is usually better fixing security flaws, I’m disappointed.
 
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LeadingHeat

macrumors 6502a
Oct 3, 2015
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Yikes. Yeah that doesn’t sound great. I wonder how many bad actors there actually are out there taking advantage of this loophole though? Regardless, I hope they get this patched soon. Sounds like it may need an iOS update, but I hope it can somehow be pushed out server-side to cover the older iOS versions.
 
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zeezun

macrumors member
Aug 19, 2020
46
164
incoming 1,2,3... *you are airdopping from your device, wrongly* (in apple's defence)
 
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An-apple-a-day

macrumors member
Mar 31, 2010
71
85
Hashing should be sufficient for this use case, as long as Apple is using something better than md5. Also the salt should be dynamically negotiated. I don't think this is a big deal at all.
 
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Eorlas

macrumors 6502a
Feb 10, 2010
964
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I feel like this isn’t news. I disabled AirDrop discovery on my devices ages ago (and only manually enable it when I need to receive something) because I read about this ages ago (like years ago, if I’m not mistaken).
according to the article, it could not have exceeded 2 years ago.
 
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Unregistered 4U

macrumors 601
Jul 22, 2002
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Yeah that doesn’t sound great. I wonder how many bad actors there actually are out there taking advantage of this loophole though?
Even though this obviously needs to be patched, does anyone seriously believe that any "bad actor" is going to go through this much work so he can sit in a Starbucks and steal someone's phone number? :)
No :) Folks need to remember that their life REALLY isn’t actually all that interesting, anyone interested IN their information is not going to waste time on an AirDrop brute force hack. If they are THAT close and REAAAAAALLLLY want your information, they can readily get access to it using one of the devices below.
7AC36103-32DC-4AF4-840B-2C78255852CD.jpeg
 
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Unregistered 4U

macrumors 601
Jul 22, 2002
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Researchers at TU Darmstadt have discovered that the process which AirDrop uses to find and verify someone is a contact on a receiver's phone can expose private information.
Namely, their email address and telephone number. Not their bank account data, not their social security number. Notice how they obfuscate “PRIVATE DATA OOOH SCARY” from what’s actually shared.

There is a VERY VERY good chance that your “private data” in this case is already on a list some ne’er do well purchased last month… and they didn’t even have to be within AirDrop range to get it! Next they’ll be reporting that
“Folks can gain access to your email address by ASKING you for it. If you fall for the exploit and provide them with your email address THEY WILL HAVE IT!! We reached out to Apple asking if they plan to stop providing email addresses so that people aren’t able to leak them and they looked at us funny and shooed us away.”
 
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ikramerica

macrumors 6502a
Apr 10, 2009
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Namely, their email address and telephone number. Not their bank account data, not their social security number. Notice how they obfuscate “PRIVATE DATA OOOH SCARY” from what’s actually shared.

There is a VERY VERY good chance that your “private data” in this case is already on a list some ne’er do well purchased last month… and they didn’t even have to be within AirDrop range to get it! Next they’ll be reporting that
“Folks can gain access to your email address by ASKING you for it. If you fall for the exploit and provide them with your email address THEY WILL HAVE IT!! We reached out to Apple asking if they plan to stop providing email addresses so that people aren’t able to leak them and they looked at us funny and shooed us away.”
I am pretty sure you can get all that juicy data by putting a name in a google search. Plus home address, previous addresses, criminal record, etc.

I do think the odds of someone brute forcing an airdrop in close
proximity to you in order to discover your phone number and email is pretty remote. One assumes that if they are going to all that effort to target you, they already know your name.

One question for the researchers: does this mean turning on “everyone” is more secure as no matching is attempted?
 
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