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Password hashes can be
stolen in many ways,

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for example via SQL injection
attacks on a website

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that extracts the hashes
from the data base.

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A SQL injection attack
happens when a website

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does not validate the input
of the data it receives,

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and because of that,

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you can send direct queries

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to the data base and ask it,

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“Would you mind very much

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just to give me your
password hashes?”,

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in the worst case scenario.

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And here, what you can
see here is a website

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that has a collection of hashdumps
from compromised websites.

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You can see LinkedIn, EHarmony,
the dating website.

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These are the hashing
algorithms they use,

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MD5, not very good,
should not have used it;

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SHA1, also not acceptable.

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So you can see, even big
sites doing it wrong.

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And then you’ve got
an analysis here,

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so we can check that out.

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I’m going to go down here

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and you can see here,

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based on this analysis,

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you feed into your
cracking process.

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You can see here

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there’s a significant amount that
uses the word LinkedIn,

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so you would feed
that into your rules.

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And the rest of this
sort of information,

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like the Length, the Character
sets used,

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Character set frequency, etc.,

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that all goes back into your
recracking of the hashes.

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Hashes can also be extracted
from operating systems.

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If you have local
access to the drive,

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you can do that by mounting
the hard drive

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in another operating system,

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or using a live CD,

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as long as it can mount
the file system.

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And here we have the example
of Windows.

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We’ve got LM hashes,
we’ve got NT hash,

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NTLM hashes for the passwords
of these users here.

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And in Windows, these are stored

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in something called the Security
Account Manager

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or SAM, which is essentially
just a file.

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And those hashes

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can be extracted
with various tools.

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Here’s an example of one,
PWDUMP7,

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and you can see it here

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literally dumping the usernames
and hashes,

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and the hashes are then put
into cracking tools,

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which I’m going to show
you in a second.

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Because offline attacks are not interacting
with the cryptosystem,

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they can't defend themselves,
hashes can't defend themselves,

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they’re just a bunch
of characters in a file.

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So the attack can be many,

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many, many times faster
than online attacks.

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So think about

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in the region of one hundred billion
guesses per second

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or maybe one hundred trillion
guesses per second

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with super multi GPU crackers

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like the one you can see here.

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And it’s this speed
which enables

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brute force hybrid
and custom attacks

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that we have gone
through to work

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with moderately complex
passwords.

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In Kali you’ll see that there are
actually lots of cracking tools.

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We go down to here,
Password Attacks;

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got Hashcat, John the Ripper,

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Ophcrack, there’s wordlists
or dictionaries there,

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and there’s other tools
beside these as well.

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Let me introduce you to Hashcat.

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So we need some hashes
in order to crack first,

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so I’ve downloaded
some public hashes

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from one of the old crack sites

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that I’ve just chosen at random.

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And this is the file here,
hashes.txt,

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so I will just (00:03:15 – inaudible)
that so you can see it.

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So there you go,

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you can see all of
the hashes there.

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Stop that for a minute.

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So we’re going to crack these

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and work out what
the password is

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for each of these hashes.

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Sometimes you won't know

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what sort of hash
or key derivation,

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combination that you have,

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so you can try using
hashid with a hash

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and see what sort of
results you get.

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And we can see here

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that this is possibly a number
of different hashes,

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but I actually know
that this is MD5.

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We’re going to use a wordlist
or dictionary attack

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as part of a kind
of hybrid attack,

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so here’s our dictionary,

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this is what this looks like.

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See, lots of common words that
people use for passwords,

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you can see, it’s not
actually that big.

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And here’s a command,

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we’re going to use
“hashcat” with “-m”

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is to tell it that it’s MD5.

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Those are the hashes,
that's the wordlist,

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and that’s just simply
the output file.

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Let's give it a go,
see what we get.

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So the wordlist has
successfully cracked

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22,000 out of five hundred
odd thousand hashes,

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that’s about 4%,

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and that was literally
in a few seconds

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with a dictionary attack.

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And here we are,

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same command,
but with “-a 1”,

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1 for Hashcat is
a combination attack.

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Press "S” for status,

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we can see it there
cracking more files.

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So click there.

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Remember this file here,

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this is how we can
potentially add rules,

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so we can take our dictionary
without input words

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and then change them
to other words.

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So here, this would do nothing,
if we had that as a rule,

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that’d be lowercase; we can
append characters,

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we can duplicate the word;
password, password.

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So I’ve got a rules file here,

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so I’ve just added these,

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so we’ve got some appending
of characters at the end,

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we’ve got "f” a duplicate
word reverse,

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and “;” for “do nothing”.

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So let's save that,

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and we append to the end here,

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our “- - rules”,

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and then our rules file.

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Let's give that a go.

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And you can see,

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in literally just a few seconds,

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went from 22,000 to 23,000.

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So that gives you a flavor

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of the sort of process
that you go through

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when you’re doing
password cracking.

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And because these were MD5,

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these are much, much
faster to crack,

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and they would be if they’d use

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a key stretching function.

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You can even try
decrypting online,

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and there are a number of sites

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that can enable you to do that.

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Check out this link,

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it provides a bunch of sites
who enable you to do that.

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The big one is actually
crackstation.net.

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An online cracking is
actually very viable

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because it’s fast
and easy to hire

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for short periods of time,

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massively powerful servers.

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For example, with AWS
Amazon you can rent

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these for short periods of time
to crack passwords,

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which is what people do.

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It’s a time cost exercise.

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But if the right hash key
derivation function,

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key length and password
is being chosen,

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then it’s unlikely to be cracked
even with all the power.

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But sometimes you don't always
have to crack the hash.

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You can capture it and relay it
in a relay attack.

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If you’re a man in the middle,
instead of cracking it,

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you just forward it on,

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after you have captured it,

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enabling your access
to the destination.

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Famously, Windows LM
or NTLM hashes

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can be relayed due to
an authentication flaw,

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which can be done with
Metasploit in Kali.