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Comment Re: There we go again (Score 1) 383

I am going to have to side with AC-x, here, you don't have a fundamental understanding of what he is putting forth in this discussion. You seem to be defending your points without fully understanding them.

I fully understood what he put forth and repeatedly stated that it had no relation to the context of my original statement.

Dictionary attacks are not used on things that are rate limited - they are used on grabbed hashes.

Not true. A dictionary attack has no such prerequisite. Dictionary attacks are used all the time even when you have no grabbed hash. You're simply redefining the term.

Wikipedia:

In cryptanalysis and computer security, a dictionary attack is a technique for defeating a cipher or authentication mechanism by trying to determine its decryption key or passphrase by trying hundreds or sometimes millions of likely possibilities, such as words in a dictionary.

Technique
A dictionary attack uses a targeted technique of successively trying all the words in an exhaustive list called a dictionary (from a pre-arranged list of values).[1] In contrast with a brute force attack, where a large proportion key space is searched systematically, a dictionary attack tries only those possibilities which are most likely to succeed, typically derived from a list of words for example a dictionary (hence the phrase dictionary attack). Generally, dictionary attacks succeed because many people have a tendency to choose passwords which are short (7 characters or fewer), such as single words found in dictionaries or simple, easily predicted variations on words, such as appending a digit. However these are easy to defeat. Adding a single random character in the middle can make dictionary attacks untenable. Unlike Brute-force attacks, Dictionary attacks are not guaranteed to succeed.

Funny, not a single mention of a grabbed hash and I can find many such more definitions and explanations that also contain no such prerequisite.

Comment Re: There we go again (Score 1) 383

Sure, that is a problem but it's not as if any single site can prevent that. As I've said over and over again, nothing of what I have stated is perfect since there is no such perfect security measure. As stated numerous times, my comments about certain things are always within a certain context.

To offer up an analogy to the way AC-x has been attacking me: My original post would be like me talking to someone who says that it's pretty easy to pick a lock that has an external keyhole (which is certainly true in many situations), and then I come back by saying that in such a case you should have a deadbolt that has no way to be unlocked externally. AC-x then comes into the conversation to tell me about how if the person has a sledgehammer that they can just brute force there way around the deadbolt problem. I then come back and say, sure, they could also simply break a window to bypass the deadbolt as well. And then he comes back telling me about how I'm stupid and don't know anything of how deadbolts and sledgehammers work.

Now, his statement is surely true that a sledgehammer breaking through a door will certainly be able to bypass a deadbolt. He is also correct that having previously infiltrated a system you can try to offline brute force a password so that you can get in without hitting any of the mitigations I brought. But that was not the context of the response that I made to the person which was simply that of someone trying to dictionary attack a site without having any prior knowledge about the user's password (or in the hypothetical situation the person simply has a lockpick set not a sledgehammer).

Comment Re: There we go again (Score 1) 383

To add, I want to again stress that what I stated is not a catch-all for any and all potential attack vectors. It was simply made in the context of a person attempting to dictionary attack a user's password without them already having a password hash list or any other information from having previously breached your system. Anything beyond that scenario obviously requires further mitigations and procedures being in place.

Comment Re: There we go again (Score 1) 383

If they do, there are botnets that help you try lots in a short period of time.

After the first 5 failed logins you don't allow ANY logins for the cooldown period so having a botnet does't really help you. Also, it would be trivially to detect that someone is hopping from IP to IP to try to login to the same account as this would not be something a normal user would ever do. At that point you simply lock the account entirely, ban any of the IPs that continue to try to login to the account and then work from there.

Most attacks involve dumping the password hash database.

Which is a different scenario than what I was referring to. In that case you better hope you detected the attack or else you are basically fucked.

And even brute forcing is getting easier. If you need a SPECIFIC password, it's not any easier, but if you have a bunch of hashes and you want a good chunk of accounts (without caring if you have every account), it's actually easy. In fact, Ars Technica covers a domain-specific brute forcer [arstechnica.com].that relies on terminology from the sites cracked to get a list of potential passwords EXTREMELY quickly. Follow this with trivial modifications to get more. If you have a list of a million passwords, you could easily derive half of them this way, and then move on to the next list.

Brute forcing is getting easier. That is why you simply make your site an unattractive one to attack by making it so they can only do a very small amount of attempts before hitting a cooldown and then an eventual total account lock. Sure, this can be an annoyance to a user, but it's much better than their account being breached. But again, if the attacker already has a password hash list from already cracking your system, they have a much easier go at you especially if they can find out you didn't salt the hashes (or you used a weak PRNG for the salting, etc.) or do any other proper procedures.

Comment Re: There we go again (Score 1) 383

This of course assumes the administrators are paying close enough attention to notice in short order when the database has been compromised, and that all users define a secondary means of contact through which to send a reset password. It also ignores the issue that most users use the same username and password across multiple sites, such that a pair compromised on one site and invalidated as described would still be valid on another site.

A very valid concern and as I address in another post it is not a perfect solution. There is no way to prevent users from reusing passwords across sites nor will there ever be foolproof way to spot every intrusion. But then again, no security procedure is perfect and anyone stating otherwise is selling you snake oil.

And as I've had to state over and over again (and this isn't meant against you wagnerrp), my statement about rate limiting, etc. was in the context of a post that did not mention an attacker already having compromised the system and having a DB dump with all the password hashes. That is a completely distinct scenario than the one I referred to and obviously would require other mitigations.

Comment Re: There we go again (Score 0) 383

By your previous posts it seemed you needed things put in simple terms, especially since you claimed that 1) knowing the hash is the same as knowing the password (it's not) and 2) rate limiting could defeat offline password cracking (it can't). Do you stand by those claims?

Nope, because I never claimed that. You misunderstood my point and started falsely assuming things.

That's no solution: 1) Relies on the attack being detected in the first place.

Of course it is predicated on knowing you've been attacked. I was pretty sure that would be quite obvious. Of course, if you've been attacked and have no knowledge of it that these security measures won't prevent an attacker from being able to attack you again after offline brute forcing a password.

It's also completely irrelevant to the question of being able to dictionary attack a password.

And I never said it had anything to do with that scenario. You've basically have been twisting my words into something I never stated or implied and then have applied them to scenarios outside of what I originally responded to. At this point I'm simply just going to ignore you.

Comment Re: There we go again (Score 0) 383

Yes, they aren't. But all these scenarios are orthogonal to what I was responding to originally which is someone talking about using a dictionary attack to brute force password.

As I originally responded to AC-x, if the attacker already has the hash and can then brute force it, of course what I mentioned doesn't stop them, but that scenario is no different than knowing their phone's PIN and being able to side step any of the very same protections I mentioned that phone OSes use which is to use a lock-out after a certain number of failed attempts.

Comment Re: There we go again (Score 1) 383

Hey Desler I really don't get you, you (appear to) know what a salt is yet you don't understand that an attacker would be performing the attack on the hash offline, with their own hardware. Rate limiting their own hardware would be, as you put it, the height of idiocy.

Except what you are talking about was not what I was originally responding to. You basically injected yourself into the conversation and completely changed the context and then started calling me an idiot. I suggest you re-read what I originally responded to:

They can be, but it would be incredibly stupid to use something like that. A dictionary attack would crack that password in seconds.

What I do is have a single, strong password that I have stored only in my brain and all other passwords are hashed on-the-fly from that and the domain or name of whatever I need the password for. I get unique, strong password for everything, but only have to remember a single one.

Do you notice that nowhere in that quoted statement is there anything about the attacker already having the password hash?

Comment Re: There we go again (Score -1, Flamebait) 383

You probably shouldn't try to write about things you don't know about or understand.

My irony meter exploded.

1. The industry accepted way to store passwords securely in a database is with a one-way, salted cryptographic hash (using as CPU intensive algorithm as possible).

Duh. Being Captain Obvious again?

2. Many organisations have had database intrusions where these password hashes have been stolen (eg. eBay [threatpost.com], Linkedin [sophos.com], LivingSocial [arstechnica.com] etc.)

Yes, they have.

3. When this happens (i.e. "they have a copy of the password hash") passwords can be cracked offline. Strong passwords are safe (too hard to brute force), but weak passwords can be found using a dictionary attack.

Of course, this is why you lock the accounts until the user resets the password. Poof that attack vector is now gone.

4. Once the password is found offline a hacker can log straight in to the victim's online account with a single password attempt.

Only if you're system admins are dumb enough to not do what I state above.

Comment Re: There we go again (Score 2) 383

Only if the passwords haven't been salted properly. Even then, a rainbow tables attack can also be thwarted by the same techniques I mentioned above. Allowing any attacker the ability to do 10s of millions if not a couple of billion (with powerful enough hardware) tries a second to brute force a password is just the height of idiocy. Using constant time password checking, rate limiting, cooldown periods and as a last resort IP bans makes you such an unattractive target that they usually just move on to some other insecure site.

Comment Re: There we go again (Score 1) 383

Forgot to close my quote tag so fixing it.

However if a chosen password appears in a password dictionary than you can cut down your brute force search space by so much it goes from taking years (even centuries) to crack a password to taking a few hours (sometimes minutes).

Yes, that's why you stop such attacks by rate limiting and cooldowns and then eventually just ban their IP if they are just obviously an attacker. If they can only have 5 tries every 15-20 minutes the attacker is going to give up unless the user's password just happens to be near the very beginning of the dictionary.

Comment Re: There we go again (Score 1) 383

You seem to have no clue what a password hash actually is.

Nope, you're just a poor mind reader.

Yes, that's why you stop such attacks by rate limiting and cooldowns and then eventually just ban their IP if they are just obviously an attacker. If they can only have 5 tries every 15-20 minutes the attacker is going to give up unless the user's password just happens to be near the very beginning of the dictionary.

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