Top Password Cracking Techniques
Rainbow table attack
A rainbow table is a list of pre-computed hashes – the numerical value of an encrypted password, used by most systems today – and that’s the hashes of all possible password combinations for any given hashing algorithm mind. The time it takes to crack a password using a rainbow table is reduced to the time it takes to look it up in the list.However, the table itself will be huge and require some serious computing horse power to run, and it’s useless if the hash it is trying to find has been ‘salted’ by adding random characters to the password before applying the hashing algorithm.
There is talk of salted rainbow tables existing, but these would be so large as to be difficult to use in practise. They would likely only work with a predefined ‘random character’ set and password strings below 12 characters as the size of the table would be prohibitive to even state-level hackers otherwise.
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Brute force attack
This method is similar to the dictionary attack but with the added bonus, for the hacker, of being able to detect non-dictionary words by working through all possible alpha-numeric combinations from aaa1 to zzz10.
It’s not quick, provided your password is over a handful of characters long, but it will uncover your password eventually. Brute force attacks can be shortened by throwing additional computing horsepower, in terms of both processing power – including harnessing the power of your video card GPU – and machine numbers, such as using distributed computing models and zombie botnets.
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This uses a simple file containing words that can, surprise surprise, be found in a dictionary. In other words, if you will excuse the pun, this attack uses exactly the kind of words that many people use as their password.
Cleverly grouping words together such as ‘letmein’ or ‘superadministratorguy’ will not prevent your password from being cracked this way – well, not for more than a few extra seconds.
There’s an easy way to hack: ask the user for his or her password. A phishing email leads the unsuspecting reader to a faked online banking, payment or other site in order to login and put right some terrible problem with their security.
Social engineering takes the whole ‘ask the user’ concept outside of the inbox that phishing tends to stick with and into the real world.
A favourite of the social engineer is to telephone an office posing as an IT security tech guy and simply ask for the network access password. You’d be amazed how often this works. Some even have the necessary gonads to don a suit and name badge before walking into a business to ask the receptionist the same question face to face.
Savvy hackers have realised that many corporate passwords are made up of words that are connected to the business itself. Studying corporate literature, website sales material and even the websites of competitors and listed customers can provide the ammunition to build a custom word list to use in a brute force attack.
Really savvy hackers have automated the process and let a spidering application, similar to those employed by leading search engines to identify keywords, collect and collate the lists for them.
The most confident of hackers will take the guise of a parcel courier, aircon service technician or anything else that gets them access to an office building.
Once they are in, the service personnel ‘uniform’ provides a kind of free pass to wander around unhindered, and make note of passwords being entered by genuine members of staff. It also provides an excellent opportunity to eyeball all those post-it notes stuck to the front of LCD screens with logins scribbled upon them.
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It’s easy to imagine that passwords are safe when the systems they protect lock out users after three or four wrong guesses, blocking automated guessing applications. Well, that would be true if it were not for the fact that most password hacking takes place offline, using a set of hashes in a password file that has been ‘obtained’ from a compromised system.
Often the target in question has been compromised via an hack on a third party, which then provides access to the system servers and those all-important user password hash files. The password cracker can then take as long as they need to try and crack the code without alerting the target system or individual user.