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The Dropbox hack is real

troyhunt.com

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Re: The Dropbox hack is real

#201

Post by brohee »

berlam wrote: post #186
dividuum wrote: post #147

Earlier quoted context omitted.

For gmail, if you have someone@gmail.com, you can just append +anything to your address like this: someone+anything@gmail.com. It will still end up in your mailbox without having to set up anything. See https://gmail.googleblog.com/2008/03/2-hidden-ways-to-get-mo... I would assume that google apps version of gmail offers something similar.

This feature is called sub-addressing, but it is also known as plus addressing or tagged addressing. I also use it but some services do not allow the plus sign in their registration form. Very frustrating.

Rejecting addresses with a plus is to me a strong incompetence clue, so unless somehow unavoidable between two choices I chose the one allowing a '+'.

Sometime I even fire a mail explaining people rejecting '+' how and why they lost my business...

Re: The Dropbox hack is real

#202

Post by philipov »

jasonkostempski wrote: post #192
_puk wrote: post #158

Earlier quoted context omitted.

Whilst great info, unfortunately most of the sites that one would actually try to use this on don't accept addresses containing a "+" as valid. Another Google Mail trick is to use periods. Not as useful as the +, but for those sites that don't accept +, one can usually add in a few extra periods to place sites into buckets (multiple adjacent periods don't work). m.y.e.m.a.i.l@example.com

Even if they did accept it, haven't spammers figured out the pattern by now?

I don't think spammers look at individual email addresses. They're interested in 50 million emails, not you. I suspect the number of people using subaddressing is too small to notice. If it became popular enough that even computer illiterate people began using it, that's when it would be noticed.

Re: The Dropbox hack is real

#203

Post by zaroth »

> As for Dropbox, they seem to have handled this really well.

I'm biased, but I can't agree with this. From what I can tell, there are two communications from Dropbox -- one in 2012 [1] and one last week [2].

In 2012 they did not disclose that hashes were stolen, so I don't see how it's really relevant. In the latest communication, they don't actually explain the risk to the user. They say it is "purely as a preventative measure" but if salts and hashes were accessed, then that is not the case.

Just because Troy doesn't have access to some of the salts, doesn't mean the attacker doesn't have access. We don't know how many iterations of SHA-1, but SHA-1 can be run by a single GPU on the order of billions of times per second. So unless Dropbox is coming out and saying they know for certain that random 128-bit salts were definitely not accessed by the attacker, almost all of the SHA1 hashed passwords are getting cracked. Users need to know their passwords are exposed, and must be reset not as a preventative measure, but because they are almost certain to be compromised.

As for the salted/bcrypt passwords, we can see from Troy's hash they used $2a$08$ which is bcrypt with a cost factor of 8 -- 2^8 iterations. Gosney's latest rig [3] could crack these bcrypt hashes at about 105,700 / 8 = 13,212 per second. That's not terrible, but that's still 416 billion tries in a year for a modest investment.

[1] - https://blogs.dropbox.com/dropbox/2012/07/security-update-ne... [2] - https://blogs.dropbox.com/dropbox/2016/08/resetting-password... [3] - https://gist.github.com/epixoip/a83d38f412b4737e99bbef804a27...

Re: The Dropbox hack is real

#204

Post by throwawayReply »

Dylan16807 wrote: post #126
willvarfar wrote: post #56

Earlier quoted context omitted.

I actually googled before asking my question, and couldn't come up with a good feel for just how crackable these are with hashcat... I guess I don't know the terms or the prices. Is anyone able to make any sense of the GPU hashcat benchmarks that are posted? Something distilled down to "if you spend $xxx, then you can crack any salted sha1 under 12 letters+digits+punctuation in n hours if you knew the salt; if its bc…

A rough estimate for using spot instances on EC2 says you can get maybe 40 trillion SHA1 hashes per dollar. (700MH/s and just under $.07/hour) So one dollar will crack a password 7 characters long. A million dollars will crack a password 10 characters long. Switch to bcrypt and you're now at 25 million hashes per dollar on those same instances. Now you can barely crack passwords that are 4 characters long, or for a m…

This is why strong passwords are important. You can crack a lot of users with Password2016! At 25M/$.

Re: The Dropbox hack is real

#205

Post by tdkl »

wrboyce wrote: post #69
donw wrote: post #6

Since lots of people will be rotating passwords, this is probably a good time to set up Two-Factor Authentication (2FA) as well. I recommend Authy as your 2FA app, as it lets you set a backup password, which you can use to move your 2FA tokens between devices. For your critical services, keeping encrypted copies of your backup codes is a must.

I have to disagree with the Authy recommendation. I switched to Authy a few years ago, but it was nothing but painful and I have recently migrated away from it. For a long time the "TouchID Prompt" was slow and buggy, but that does appear to be fixed now. The real pain point is that it managed to corrupt one of my keys (how??) and the app tries to get me to backup my keys to their servers with multiple popups (which…

> the app tries to get me to backup my keys to their servers

That's the idea for using Authy.

Re: The Dropbox hack is real

#206

Post by midgetjones »

OJFord wrote: post #196
0x0 wrote: post #26

It was pretty obvious the dropbox hack was real several years ago, because lots of spam mail started arriving at my dropbox-unique email almost immediately after the breach. I changed my email to another unique address quickly back then. Unique-per-service email addresses work pretty well as a canary for breaches. Just make sure there is more uniqueness than just the service name to such addresses, or someone could s…

> Unique-per-service email addresses work pretty well and they're so easy with Gmail - anything following a '+' character after your username (or alias, if using your own/company domain) will go to the same box, but keep the distinct address. Unfortunately, depressingly many sites validate email fields, and get it wrong - thinking '+' is not allowed. IMO it's not even worth trying to get an email regex (or other vali…

I'm pretty sure they do know a `+` is allowed...

Re: The Dropbox hack is real

#207

Post by jrs235 »

have_faith wrote: post #143
peteretep wrote: post #25

Dropbox is about the only service I use a memorable password for, as it has my 1Password file in it, which has my Google one-time-auth codes in it. If I lose my phone while on the road, only remembering my Dropbox password is going to get me out of the mess. Any sensible other solutions here? It's still ~14 characters, but other than making it more random, what are my options?

All of my passwords are based on the website name that I'm logging in to. I have a small algorithm in my head about how to generate a password from the site name that looks at stuff like first and last letter, number of letters, some kind of prefix/suffix, etc. And I end up with a unique password around 20 characters that I don't need to remember for every website. This way I don't ever remember a password, I just re…

When one of the sites you use gets breached, you'll want/need to change your password and won't be able to use the same single algorithm. This will throw things of as you won't be able to use a single algorithm. Sure you could not use two. But you'll need to remember what sites use which one.

Re: The Dropbox hack is real

#209

Post by m0nty »

tajen wrote: post #189
m0nty wrote: post #108

Earlier quoted context omitted.

Download a password manager like Keepass, Lastpass or Password Safe: https://en.wikipedia.org/wiki/List_of_password_managers I use Keepass, it does exactly what I need. Secure the password manager itself with a long password. Put your logins into it, and generate a unique random password for each one, then go to the website in question and change the password to the new one. When you want to login to that website, op…

Is Keychain Access from OSX a safe password manager? Also, how comes all security-aware people trust 1Password and LastPass, even though they are not open source? Isn't that one of the rules of security, publish the source so we can trust it?

Another "rule of security" is that taking one step forward is better than nothing at all. So theoretically, a proprietary password manager could have a backdoor which could be used by the vendor or security services. But that's a relatively small group of people compared to "the whole world" which is where most people are with easily-guessed passwords which get reused everywhere.

Also, the idea that an army of trained security professionals is ready and able to scan open-source software for vulnerabilities isn't true - I think there was a study a few years ago which proved these security checks often didn't happen, people just assumed they did. The OpenSSH (secure shell) software was compromised for years and nobody noticed, and it is true open source and a critical part of people's systems as well.

You're looking to mitigate risks. A password manager is a step in the right direction. If you are truly paranoid (good for you) something like this, based on GPG, might be the right answer for you:

https://www.passwordstore.org/

Personally I prefer not to use cloud-based password managers because I don't know what their backend security is like. But those more knowledgeable than me might say "they're fine" because of the way the encryption is structured.

Re: The Dropbox hack is real

#210

Post by rnbrady »

midgetjones wrote: post #206
OJFord wrote: post #196

Earlier quoted context omitted.

> Unique-per-service email addresses work pretty well and they're so easy with Gmail - anything following a '+' character after your username (or alias, if using your own/company domain) will go to the same box, but keep the distinct address. Unfortunately, depressingly many sites validate email fields, and get it wrong - thinking '+' is not allowed. IMO it's not even worth trying to get an email regex (or other vali…

I'm pretty sure they do know a `+` is allowed...

I've had sites reject an email containing +.
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