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Yahoo discloses hack of 1B accounts

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Re: Yahoo discloses hack of 1B accounts

#281

Post by alyandon »

0x0 wrote: post #189
alyandon wrote: post #11

"Separately, we previously disclosed that our outside forensic experts were investigating the creation of forged cookies that could allow an intruder to access users’ accounts without a password. Based on the ongoing investigation, we believe an unauthorized third party accessed our proprietary code to learn how to forge cookies." So that exactly explains how my Yahoo account was used to send spam despite having a pa…

Are you sure they actually logged in to your account to send spam (are the spam emails visible in your sent folder), or could it be that someone is just spoofing the SMTP MAIL FROM / email From: header?

As far as I can tell it wasn't someone spoofing my email address. Emails were sent to people on my contact list and the numerous bounce messages to contacts that no longer had valid email addresses confirmed the origin of the traffic.

Re: Yahoo discloses hack of 1B accounts

#282

Post by cm2187 »

jsjohnst wrote: post #267
cm2187 wrote: post #191

Earlier quoted context omitted.

Agree, but a collision even for md5 is a relatively rare event. When brute-forcing the bcrypt hash, this would reduce the attempts you would need to try against a given hash, but only by a very small factor. With a reasonable work factor, I would assume it would still make a brute force attack impractical at scale. I didn't do the test, but I'd expect that there wouldn't be more than a handful of collisions for the m…

I've done it before on a 1 billion word / password list and didn't get any collisions.

That being said md5 does generate collisions. I was playing with the IMDB movie database that you can download. They use a combination of the title and the year as a primary key. I tried using an md5 instead to save space (but giving a reproducible ID instead if an identity column), and got many collisions. No collision with SHA256.

Re: Yahoo discloses hack of 1B accounts

#283

Post by manarth »

leereeves wrote: post #273
manarth wrote: post #266

Earlier quoted context omitted.

> "Passing the password through MD5 reduces the complexity to 128 bits, you can't get that back." Assuming that the new hash is secure (and sha512 is generally agreed to be secure), then, given a specific sha512 hash, the original MD5 hash can only be determined via rainbow tables, which is a Big-O operation. Even though entropy is reduced, it's still a significant work to determine the original MD5 hash (significant…

In this case an attacker isn't looking for a collision (which would mean creating two passwords with the same hash, and what hash that is doesn't matter). The attacker needs a password with a specific hash, and the best reported attack for that is around 2^128.

Agreed, that the best reported rainbow-table attack on MD5 is 2^128 (i.e. the complete range of possible MD5 hashes).

Personally, I'm willing to chance that my password will be discovered via a brute-force attack within the next 0.65 billion billion years [1]

[1] http://bitcoin.stackexchange.com/questions/2847/how-long-wou...

Re: Yahoo discloses hack of 1B accounts

#284

Post by [deleted] »

Helmet wrote: post #268
234dd57d2c8db wrote: post #254

Earlier quoted context omitted.

... "offshore workers" are not a race. You realize offshore workers could be the same race as the person posting right?

Given the context, you know damn well what he means - it's coded speech and I refuse to believe that you're that naive.

[deleted]

Re: Yahoo discloses hack of 1B accounts

#285

Post by tomc1985 »

For the longest time my yahoo account (which I had not checked on in many years) reported at least a dozen open sessions originating from IPs in Russia and Eastern Europe, and unlike my legit sessions I was unable to kill them in the control panel (the site would bug out)

So yeah, Yahoo's been hacked. Duh...

Finance and Flickr are about all Yahoo is good for any more, and I think my portfolio page loads (instead of 404'ing) maybe 1/2 the time I request it...

(God I really hope they dont mess with flickr though...)

Re: Yahoo discloses hack of 1B accounts

#286

Post by cm2187 »

user5994461 wrote: post #278
cm2187 wrote: post #141

Earlier quoted context omitted.

But would it require users to change their password? The way I would have implemented it, but would be keen to know how secure it is, is that you start with the md5 of the password ( md5(password) ). You then bcrypt or scrypt that md5 ( bcrypt(md5(password)) ) and replace the md5 in your database with the bcrypt hash. When a user logs in, all you need to do is to calculate the md5 first then check that md5 against th…

It's one way to do it, which is okay sometimes. The other way is to add a new empty column for bcrypt. The next time the user logs in, you save the bcrypt hash and you remove the MD5 hash. Over time, the active users will be migrated to the new scheme. The only issue is the abandoned accounts, they'll keep the old weak scheme.

I am not sure I agree. Your way will leave all the non active users exposed in the case of a leak. They may not be active on your website but are likely active on another website using the same password.

Re: Yahoo discloses hack of 1B accounts

#287

Post by user5994461 »

yuhong wrote: post #95
pluma wrote: post #83

Earlier quoted context omitted.

As a data point: when I was a teenage code monkey in 2004 writing PHP I already understood that unsalted MD5 is unsafe. According to Wikipedia: * 2004 it became possible to find MD5 collisions at a rate of one per hour on a cluster * 2005 it became possible to do this within "a few hours" on a consumer laptop * 2006 it became possible to do this within one minute * nowadays it's possible to do this "within seconds" P…

MD5 collisions are probably not important for passwords.

To put it in layman terms.

The MD5 collisions attack usually done by researchers: They want to generate 2 files with the same MD5 hash (they can put anything they want in these files).

This kind of attack doesn't affect passwords. The user picked one file (i.e. the password), you don't know it, you can't change it, you can't choose it.

Re: Yahoo discloses hack of 1B accounts

#288

Post by WillPostForFood »

mlangdon wrote: post #272
234dd57d2c8db wrote: post #254

Earlier quoted context omitted.

... "offshore workers" are not a race. You realize offshore workers could be the same race as the person posting right?

This is technically true, which is the best kind of true. Swap in nationalist, chauvinist. It's utterly clear what was meant by racism above, in spite of your semantics.

Yes we understand, racist is the liberal catch all for anyone you disagree with. The problem is that it dilutes the value of the word, so when someone deserves to be called racist, it people don't know if they really are racist, or are just opposed to outsourcing jobs.

Re: Yahoo discloses hack of 1B accounts

#289

Post by curiousDog »

sqldba wrote: post #230

Technically; no. Bureacratically; maybe. Given the skill and self direction of offshore workers; impossibly.

While some offshore workers might not be MIT grads (/s) like you, branding them all as an incompetent group is neither fair nor correct. If offshoring didn't provide tangible value to the US IT industry it would've been shut down a while ago.

Re: Yahoo discloses hack of 1B accounts

#290

Post by jsjohnst »

cm2187 wrote: post #282
jsjohnst wrote: post #267

Earlier quoted context omitted.

I've done it before on a 1 billion word / password list and didn't get any collisions.

That being said md5 does generate collisions. I was playing with the IMDB movie database that you can download. They use a combination of the title and the year as a primary key. I tried using an md5 instead to save space (but giving a reproducible ID instead if an identity column), and got many collisions. No collision with SHA256.

Oh, of course md5 has collisions. It's relatively easy (not computationally easy, but there are known methods) to find two random strings that hash to the same value, it's just very difficult to find a string that hashes to the value of a specific other string.
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