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Dropbox Is Probably Not Stealing Your Files

one.darrenpmeyer.com

21–30 of 105 posts

Re: Dropbox Is Probably Not Stealing Your Files

#21
Quote:

"A simple protocol can give us an idea of whether data is being sent to Dropbox:

1. Create a large-ish file (1MB) outside of the Dropbox folder

2. Monitor the network usage of the Dropbox application to see if it sends enough data that it could be that file

3. Repeat with many different files, etc.

Doing exactly that, Dropbox only sent a few hundred KB after “accessing” the target file. Seems unlikely that Dropbox is uploading files outside your Dropbox folder."

This test approach has a problem. A more realistic test would be to place a well-compressed file, one that by definition cannot be made smaller, on Dropbox and see what the system traffic size is for that file. For an optimally compressed file, if the system is reading the entire file, the read size will more or less equal the file size.

Re: Dropbox Is Probably Not Stealing Your Files

#22
post #9

Surely tradition requires that the title of this piece be "Is Dropbox stealing your files?". I mean, it's a complete waste of a Betteridge event.

It's in response to an earlier-submitted article: https://news.ycombinator.com/item?id=9136546

That is, in fact, titled in the correct manner. Maybe Betteridge doesn't count if the thrust of the article is actually to point out that "no" is the correct answer. I hadn't thought of that.

Re: Dropbox Is Probably Not Stealing Your Files

#23

Well, dropbox could just listen for fs events inside the DropBox folder; and it should, from a performance perspective as well as from a privacy point of view. And then "sends a few 100 kByte"? I hope this is a typo; if not, I would like to know what these are. (also: the OP's largish file (1MB) could easily fit into "a few 100kByte" after compression)

Actually, it cannot for the shell extension for the checkboxes over synced files. It needs to look at every file seen with Explorer to do that.

Really? The shell extension could just ask the dropbox daemon if something is known about file x/y/z, and the daemon would answer "no" if the file is outside its folder. No need to look into the file for that. Or did I miss something?

Re: Dropbox Is Probably Not Stealing Your Files

#24
post #4

This is a fine post, but all I can think about this situation is "or, you could just reverse the Dropbox client and find out for sure". Speculation about Dropbox stealing files seems premised on the idea that you can't know what the client is doing. But that's not even close to true. People reverse much, much harder targets than Dropbox for fun. If any version of Dropbox published to its user base ever did anything l…

[deleted]

Re: Dropbox Is Probably Not Stealing Your Files

#27
As an aside, I've been using Sparkleshare (built on GIT and SSH) lately. It's pretty good, and sucks up less battery on my MBP than the Dropbox client (maybe because it's not watching every file in the system!) And not only is it open source, but you can see a log of all the git commands and fix things manually if necessary.

My only lament is that it doesn't work that well over the intermittent connections. It'd be neat to have something robust like mosh (https://mosh.mit.edu) for file sync.

Re: Dropbox Is Probably Not Stealing Your Files

#28
The cycle of security is this:

1. Security experts see a security hole and note that it could only be used by a widely trusted company or government.

2. People note that it's also possible that it's not happening, and claim that the widely trusted company or government would never use the security hole.

3. It is discovered that the widely trusted company or government has been using the security hole.

Re: Dropbox Is Probably Not Stealing Your Files

#30
This article makes me irrationally annoyed by how lazy the author was. I was able to produce a test in under 5 minutes that disproves the article's core assumption:

> The Dropbox application uses a filesystem monitor to detect when changes are made by monitoring filesystem write events. This is, by necessity, a system-wide process. So DLP alerting that Dropbox is “acccessing” a new file shouldn’t be surprising.

THAT IS NOT HOW THAT WORKS!

Sorry, I am calm now. As someone who has spent quite a lot of time using Windows' File System Watcher functionality, I know that that is nonsense. Windows monitoring/watching is conducted at the kernel, when an IO operation occurs that hits a registered monitor it fires off an event (windows message) to that process to let it know, the process itself never accesses that file directly.

But just test it for yourself.

1) Download Process Monitor [0]

2) Start Process Monitor, turn off Registry, Network, Profiling, and Process events.

3) Set the include (included processes to monitor) to [whatever executable you build]

4) Build this (see examples section) [1] in C#/VB.net and run it

5) Set the process name in #4 in the include in #3

6) Write to a file in C:\ (that's the default in the example program/source)

7) You should see some Console.WriteLine() output indicating the file watcher is working. If not run as administrator.

8) There you go. As you can see, no direct file accesses to the file. The monitor events are fired as you can see, but the file remains untouched directly by your program.

The author could have done this. Why didn't they? It isn't like I had to even write one line of code or have some kind of specialist knowledge of low level kernel functionality...

PS - I don't know/care if DropBox is stealing your stuff. I just wish the article's author had at least fact-checked before they claimed that "that is how this works!!!" when in reality that is untrue. That is how it works for Anti-Virus because AV scans within files to see contents, it isn't how it works for most processes which just use the file watcher functionality. If DropBox chooses to look inside files, then why? There is no need for that.

PPS - If DropBox do have a system wide file watcher, that is just lazy. It will reduce system performance, and they could have just as easily set it up to point just to folders DropBox is configured to watch.

[0] https://technet.microsoft.com/en-us/sysinternals/bb896645

[1] https://msdn.microsoft.com/en-us/library/system.io.filesyste...

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