It’s a potential nightmare scenario:You need to open a PDF document so you double click on it to open it as usual. But instead of opening the document, a little screen comes up asking you to enter the password for the file.
Panic sets in – you were maybe given the password in an email but you can’t remember what the access code.
Of course, this never happens when you’ve got time on your hands or with unimportant files. It waits until your boss wants the information. Now! This minute! It’s doubly embarrassing if it’s your own password that’s been forgotten.
So what do you do?
If the document is your own and you’re a normal human being and regularly use one of a handful of different passwords, you go through those. With luck, the document is open. If it’s a file that someone else sent you, then you’re in deeper trouble.
The two main methods of cracking open files are called dictionary attacks and brute force. A dictionary attack does exactly what it claims. It goes through a dictionary from A to Z, testing each word in turn. The bigger the dictionary, the better the chance it has of winning this. Especially if it includes lots of peoples names – these are often used as all or part of a password.
A brute force attack is a bit like using a shot gun to shoot off a padlock – as seen in all the best westerns. It goes through every possible combination, starting with short passwords and working its way up to longer and longer ones. You could do either of these by hand but it’s a lot easier and quicker to use software instead.
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