Is your password truly secure? You may think it is and we’ve all heard the

advice about what you shouldn’t use as a password. There are loads of tools

that say they can assess just how secure your password is but these are rarely,

if ever, that accurate. There is only one way to truly test the strength of your

password and that is to attempt to break them.

In this chapter, we are going to look at a popular tool that is used by genuine

hackers to crack passwords and I’m going to show you how to use it on your

passwords. If your passwords fail, we’ll look at how to pick stronger ones.


Setting Hashcat Up


Hashcat is the name of the tool we are going to look at. Officially, it is meant

for the recovery of passwords but it is, more often than not, used as a way of

cracking passwords that have been stolen from servers that aren’t perhaps the

most secure. This makes it a great tool for testing out your own password

security.

    1. First, download Hashcat – you can get it from hashcat.net

    2. Now extract the files and save them in your downloads folder


The next step is to get some more data for the tool. We need a word list, a large

database that contains passwords and this is what Hashcat will use as its

starting point.

    3. Download rockyou.txt and save it to the Hashcat folder – do make sure

it retains the name “rockyou.txt”


Next, we have to generate some hashes and to do that we need to use WinMD.

This is freeware tool that uses little in the way of resources and it will hash

certain files.

    4. Download WinMD5

    5. Unzip the file and save it to the Hashcat directory

    6. Create two new files – password.txt and hashes.txt and save both to the

Hashcat directory

That completes the setup of Hashcat.


A Little History Lesson


Before you actually go ahead and use Hashcat, let’s look a little into how

passwords get broken and how we arrived at this point. Way back in time, long

ago in the history of computer science, passwords used to be stored by a

website in plain text. That kind of makes sense – that website has to verify that

the right password has been used. The most obvious way of doing that is to

maintain copies of all the passwords, perhaps in a file, and then check inputs

against what you have stored. That sounds easy, right?

Sadly, it was the biggest disaster in computer history. Hackers could use

devious methods of getting access to the server and would then make off with

the list of passwords. They could then log in to each account and do significant

amounts of damage, especially if the website were a financial one, like online

banking. As the security researchers recovered from what was clearly a

massive disaster, they decided that things needed to be done in a different way

and that is where hashing came in.

For those who need a refresher or who don’t know what they are, hash

functions are codes that take a small bit of information and mix it all up in a

mathematical way, so that it is nothing more than fixed length gibberish. We

call this hashing data and what is really cool about is that these hashes can only

go in one direction. While it may be easy to take some information and work

out what its unique hash is, it isn’t very easy to take the hash and work out

where it was generated. In fact, if you were using random passwords, you

would need to try every combination you could think of, and a few more

besides, and that is pretty much impossible.

So, you may have figured out that hashes have got some useful properties when

it comes to password applications. Instead of just storing a password, you will

store the hash of that password instead and, when you need to verify a

password, you would hash it, then delete the original and check it against all

the hashes on your list. Hash functions will all provide the same result so you

can verify that the correct password has been submitted. Crucially, the plain

text passwords will never be stored on a server and that means they can never

be stolen by hackers – all they will get is hashes, which are useless to them. In

response, hackers have spent a lot of time and effort trying to find ways to

reverse hashes.


How Hashcat Works


There are several things that the hackers came up with and one of them is the

way that Hashcat works. This is the most robust method because it notices that

users tend to be very unimaginative and use the same kinds of passwords.

For example, many passwords are made up of a couple of English words,

maybe a number or two and a few random capitalizations thrown in for good

measure. Some are more popular than others, such as “password” your

username, “Hello”, etc. In the same vein, many people use the names of their

pets, the year, and so on. When you know this information about someone you

can easily start to come up with some very likely guesses about what the

passwords might be and, while this might sound hopeless, don’t forget that a

computer can search through millions of passwords in just seconds.

So, what we are going to do now is imagine that all your passwords have been

hashed and a malicious hacker has stolen the list of hashes. You are that

malicious hacker and you are going to use Hashcat to try and crack the

passwords. This is a great way to test out your home security and see where

the weaknesses are in your passwords.


How to Use Hashcat


First, you must generate those hashes.

  1. Open WinMD5

  2. Open the password.txt file you created – this must be in Notepad

  3. Input one of your passwords and save the file

  4. Now open it with WinMD5

  5. You will see a small box which has the hash of the password in it Copy

     that hash into the hashes.txt file

  6. Save it

  7. Now repeat this with all your passwords, making sure to put each hash

     onto a new line in the hashes file

  8. Lastly, save a password called Password and put that hash as the last

     line in the hashes file

I will just point out here that MD5 isn’t really the best format for hash storage

– it is fast to compute and that makes brute force attacks much more likely to

succeed. But, for you, for the purposes of this exercise, this is a good thing


because you are going to be carrying out destructive testing. In a real scenario

of a password leak, passwords would be hashed using Scrypt or another

secure hash function and these are slower to test out. With MD5, we are

simulating the use of a great deal more processing power and a lot more time

than we would normally have available.

Let’s continue.

  9.  Ensure that your hashes.txt file has been properly saved and open

      Windows PowerShell (just type PowerShell in the command bar)

  10. Go to the Hashcat folder (use cd. to go up a level, ls to list the files and

      cd (name of file) to get into a file in the directory

  11. Type in ./hashcat-cli32.exe -hash-type=0 -attack-mode=8 hashes.txt

      rockyou.txt

What you have done here is said that you want the Hashcat application to run,

to put it to work on the MD5 hashes, use a mode of attack called “Prince” (a

number of strategies that will come up with variations on the words in the list)

and then to try to break the entries in hashes.txt while using rockyou.txt as the

dictionary. And breathe!

  12. Press Enter and, when the EULA comes up, accept it and then let the

      program run.

Almost straightaway, you should see the hash for Password appear and then

you just have to wait. If you have a fast computer, weak passwords will show

up within a minute or so while mediocre to normal passwords will take

anything from a couple of hours to a couple of days. Strong passwords can take

forever.

Leave this to run as long as you want, at the very least leave it overnight or

when you go out for the day. If you get to 24 hours and your password hasn’t

shown up, it's most likely strong enough for most things BUT this is not

guaranteed. Some hackers will have separate computers running this program

for days and weeks on end or they may be using a much more comprehensive

word list so, if you have even the slightest doubt about your password, change

it to a stronger one.

Your Password Broke


Most likely, at least one of your passwords broke so how do you go about

making a stronger one? One of the best and most popular of all the techniques

is pass-phrases. Open a book, any book, and then open it to a random page.

Take the first adverb, noun, adjective or verb that you see and memories it.

Now find another three or four. Put all four or five words together – no spaces,

no numbers, no capital letters and no special characters. I will tell you what

not to use – “correcthorsebatterystaple” has suddenly become a very popular

password and is now included on most wordlists!


Believe it or not, even though these are just random words, they are far easier

to remember as a password than a whole bunch of letters and numbers and way

more secure. Native English speakers can choose from a vocabulary of about

20,000 words and that means four or five randomly chosen words from those

results in billions of combinations, well beyond the reach of any of the brute

force attacks in use today.


Of course, you always have the option of a password manager. These can

generate passwords that are secure and whenever you need one and all you

need is one master password to unlock them. You do need a strong master

password and god help you if you forget it! This does giveyou another layer of

security, though, should your hashes ever be leaked.


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