The top ten password-cracking techniques used by hackers

Think your passwords are secure? Think again

list of poor passwords on notepad

Understanding the password-cracking techniques hackers use to blow your online accounts wide open is a great way to ensure it never happens to you.

You will certainly always need to change your password, and sometimes more urgently than you think, but mitigating against theft is a great way to stay on top of your account security. You can always head to to check if you're at risk, but simply thinking your password is secure enough to not be hacked is a risky position to take.

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So, to help you understand just how hackers get your passwords, secure or otherwise, we've put together a list of the top ten most popular password-cracking techniques used across the internet. Some of the below methods are certainly old-fashioned, but that hasn't diminished their popularity.

The top ten password-cracking techniques used by hackers:

1. Dictionary attack

The dictionary attack, as its name suggests, is a method that uses an index of words that feature most commonly as user passwords. This is a slightly less-sophisticated version of the brute force attack but it still relies on hackers bombarding a system with guesses until something sticks.

If you think that by mashing words together, such as "superadministratorguy", will defend you against such an attack, think again. The dictionary attack is able to accommodate for this, and as such will only delay a hack for a matter of seconds.

2. Brute force attack

Similar in function to the dictionary attack, the brute force attack is regarded as being a little more sophisticated. Rather than using a list of words, brute force attacks are able to detect non-dictionary terms, such as alpha-numeric combinations. This means passwords that include strings such as "aaa1" or "zzz10" could be at risk from a brute force attack.

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The downside is this method is far slower as a result, especially when longer passwords are used. However, this style of attack is usually supported by additional computing power to cut down hacking time, whether that's through assigning more CPU resources to the task or by creating a distributed processing farm, similar to those used by cryptocurrency miners.

3. Rainbow table attack

Rainbow tables might sound innocuous, but they are in fact incredibly useful tools in a hacker's arsenal.

When passwords are stored on a computer system, they are hashed using encryption - the 1-way nature of this process means that it's impossible to see what the password is without the associated hash.

Simply put, rainbow tables function as a pre-computed database of passwords and their corresponding hash values. This will then be used as an index to cross-reference hashes found on a computer with those already pre-computed in the rainbow table. Compared to a brute force attack, which does a lot of the computation during the operation, rainbow tables boil the attack down to just a search through a table.

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However, rainbow tables are huge, unwieldy things. They require a serious amount of storage to run and a table becomes useless if the hash it's trying to find has been "salted" by the addition of random characters to its password ahead of hashing the algorithm.

There is talk of salted rainbow tables existing, but these would be so large as to be difficult to use in practice. 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.

4. Phishing

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 log in page associated with whatever service it is the hacker wants to access, requesting the user to put right some terrible problem with their security. That page then skims their password and the hacker can go use it for their own purpose.

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Why bother going to the trouble of cracking the password when the user will happily give it to you anyway?

5. Social engineering

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 call an office posing as an IT security tech guy and simply ask for the network access password. You'd be amazed at how often this works. Some even have the gall to don a suit and name badge before walking into a business to ask the receptionist the same question face to face.

6. Malware

A keylogger, or screen scraper, can be installed by malware which records everything you type or takes screenshots during a login process, and then forwards a copy of this file to hacker central.

Some malware will look for the existence of a web browser client password file and copy this which, unless properly encrypted, will contain easily accessible saved passwords from the user's browsing history.

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7. Offline cracking

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.

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Often the target in question has been compromised via a 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.

8. Shoulder surfing

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, giving them the opportunity to snoop literally over the shoulders of genuine members of staff to glimpse passwords being entered, or spot passwords that less security-conscious workers have written down on post-it notes or in notepads. 

9. Spidering

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.

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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.

10. Guess

The password crackers best friend, of course, is the predictability of the user. Unless a truly random password has been created using software dedicated to the task, a user-generated random' password is unlikely to be anything of the sort.

Instead, thanks to our brains' emotional attachment to things we like, the chances are those random passwords are based upon our interests, hobbies, pets, family and so on. In fact, passwords tend to be based on all the things we like to chat about on social networks and even include in our profiles. Password crackers are very likely to look at this information and make a few – often correct – educated guesses when attempting to crack a consumer-level password without resorting to dictionary or brute force attacks.




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