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submitted 5 months ago by misk@sopuli.xyz to c/technology@lemmy.world

cross-posted from: https://sopuli.xyz/post/12670977

iPhone owners say the latest iOS update is resurfacing deleted nudes

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[-] mojo_raisin@lemmy.world 139 points 5 months ago

Nothing sinister, we just don't delete what we say we delete. Instead we keep it in your profile to feed the algorithms and set the "deleted" flag to make you think it's gone.

[-] cyrus@sopuli.xyz 68 points 5 months ago

I mean, to be completely fair, that's how data storage works.

We cannot really just make data disappear, so we let it get overwritten instead

[-] mojo_raisin@lemmy.world 23 points 5 months ago

But clearly the data is not overwritten and this was intentional. How do I know? Because that would amount to a massive amount of data, if it was de to a bug in Apple software or underlying filesystems, it would be detected in monitoring systems "Hey, we're using 10x the data we should be, maybe we should look into it".

The mistake was in the flag code that was supposed to fool us.

[-] cyrus@sopuli.xyz 49 points 5 months ago

no when I say "overwritten" I mean that the area is set as deleted in the filesystem and the next time something writes to that area the data that was there before is disregarded.

[-] barsoap@lemm.ee 0 points 5 months ago

and the next time something writes to that area the data that was there before is disregarded.

A single overwrite might not be enough to defeat physical forensics because shadows of the old data persist in how the new data is stored. Also when it comes to SSDs you might be waiting a long time for the data to get overwritten as the drive will wear-level its erm sectors (what are those things called with SSDs?).

[-] kaboom36@ani.social 1 points 5 months ago

They are called cells IIRC

[-] lurch@sh.itjust.works 13 points 5 months ago

the shred command in Linux tries to do this, but it may not work if the hardware moves rewritten data blocks around to mitigate wear.

[-] tal@lemmy.today 8 points 5 months ago* (last edited 5 months ago)

shred doesn't even necessarily work at the OS level. If you use something like ext3 and I assume ext4, normally when you overwrite data in a file, you're not overwriting data even at the logical level in the block device. Journalling entails that you commit data to somewhere else on the disk, then update the metadata atomically to reference the new data.

It was more-practical in an era of older filesystems.

[-] Forester@yiffit.net 11 points 5 months ago* (last edited 5 months ago)

Proper deletion should include writing all ones or all zeroes to the block but y'all be lazy as fuck.

[-] cm0002@lemmy.world 29 points 5 months ago* (last edited 5 months ago)

Only necessary on the ol spinning rust, with SSDs not only is it completely unnecessary, but it also burns extra writes.

Spinny's store data magnetically on the platter with 1s and 0s, SSDs store data on the NAND as a held charge. If there's a charge in the block it's a 1 if there's no charge it's a 0.

With spinny's, a file gets marked as "deleted" but the residual magnetic 1s and 0s will remain on the platter until eventually overwritten

With SSDs a file gets marked "deleted" and within no more than a few minutes TRIM comes along and ensures the charge on the NAND is released for that data, there's no residuals to worry about like with spinny's and is in fact necessary to ensure decent lifespans.

[-] brbposting@sh.itjust.works 3 points 5 months ago

Wow, the SSD can hold the charges perfectly while unplugged for ages? Amazing.

In a post apocalyptic world where I am in charge of building a storage drive and I’m given all the instructions and fabs, the world is going without storage.

[-] davidgro@lemmy.world 13 points 5 months ago

Wow, the SSD can hold the charges perfectly while unplugged for ages? Amazing.

Yup. Before flash memory, devices like video game cartridges which had game saves actually needed a battery to power the memory holding the saves.

[-] Drummyralf@lemmy.world 3 points 5 months ago

I want a spinny as a pet now. Sounds cute.

[-] Verat@sh.itjust.works 2 points 5 months ago

But wouldn't TRIM be the deleting he is requesting? Removing the charges would be setting all the bits in that block to the same value.

[-] AProfessional@lemmy.world 10 points 5 months ago* (last edited 5 months ago)

That just makes no sense to do, modern storage is write limited. As long as you used encryption the old bits mean nothing to anyone but you.

[-] catloaf@lemm.ee 3 points 5 months ago

SSDs are. Big storage is not using SSDs.

[-] EvilBit@lemmy.world 8 points 5 months ago* (last edited 5 months ago)

I’m not an expert, but wouldn’t proper deletion be writing random ones and zeroes to the block? Multiple times?

[-] catloaf@lemm.ee 4 points 5 months ago

I don't think it's been shown to make a difference.

[-] EvilBit@lemmy.world 4 points 5 months ago

It certainly feels more deleted…

[-] sugar_in_your_tea@sh.itjust.works 2 points 5 months ago

It was sort of true in the past, but not anymore. I think writing random data once is probably fine, even for most state level actors.

[-] cyrus@sopuli.xyz 3 points 5 months ago

yeah cuz for normal, day-to-day use that's exponentially slower the more you're deleting

You can do that when you wipe something.

[-] Forester@yiffit.net 0 points 5 months ago

Yeah, such as sensitive photos

[-] foggy@lemmy.world 2 points 5 months ago

Nitpick: it should be fuzzed with random 0s and 1s.

[-] solarvector@lemmy.zip 4 points 5 months ago

That's skipping over the fact that recovering deleted data, even if it isn't overwritten, is not an "oops". It it takes extra effort, and if that data isn't being protected it would be overwritten incidentally as drives are used.

There is a big difference in a database between "flagging" data and actually removing the association of the data to the database.

[-] pete_the_cat@lemmy.world 1 points 5 months ago

The data just needs to be overwritten to be truly deleted.

[-] sugar_in_your_tea@sh.itjust.works 18 points 5 months ago

That's how a lot of people handle deleted data in database, it's literally just a flag. That's why there's a recommendation to edit Reddit posts before deleting them, to ensure they're actually overwritten so they can't just be restored.

[-] fishpen0@lemmy.world 10 points 5 months ago

Every time someone says something like this I have to explain CDC and regular old backups. There’s no way in hell Reddit doesn’t keep cold and hot backups of their shit. And while Reddit is unlikely to be doing CDC for soc2 or other compliance reasons, it’s the easiest method to capture data for analytics purposes.

CDC stands for change data capture. It’s generally done with databases by streaming the change log or ref log to a bucket or a service like Kafka where you can fast forward and rewind the log queue to see the state of the DB at any point in time. Even if you edit your comments it’s likely sitting in a Kafka topic or a snowflake bucket outside of the DB or cache used for the presentation layer.

Zero large scale websites operate with a truly single data store. There is always another layer that your user operations don’t impact

[-] sugar_in_your_tea@sh.itjust.works 2 points 5 months ago

Yes, that's certainly possible, but it's also out of my control. I have basically three options:

  1. Delete account - we know this doesn't delete comments
  2. Delete comment - "seems" to delete comments, but we've seen comments get restored - so probably using a "deleted" flag
  3. Edit comment with nonsense and when delete - should poison comment if they're just using the deleted flag

That's it. There's no guarantee it works, but it has a much higher chance of working than the other two.

And there's a good chance they delete old backups. Hosting every edit is expensive, so there's a decent chance they clean up old data after some months.

[-] fishpen0@lemmy.world 3 points 5 months ago

In 2019 the total size of the text stored by Reddit was only 50TB. A Petabyte of data in cold storage is only 12k a year so even if they 500x in size since 2019 (very unlikely) it’s a drop in their ARR. given they sell the data for advertising and for AI, they are not deleting it. Reddit also self hosts a lot of their infra (they used to present their architecture at kubecon) so the storage costs would be even lower

[-] FierySpectre@lemmy.world 5 points 5 months ago

Funny how you think an edit doesn't write the old record to a comments_old table

[-] sugar_in_your_tea@sh.itjust.works 2 points 5 months ago

Well, there's a non-zero chance they were too lazy to implement that.

[-] Thann@lemmy.ml 1 points 5 months ago

They don't care about your security or privacy, they care about being the exclusive vendor of your personal information.

this post was submitted on 15 May 2024
513 points (97.4% liked)

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