If you were on the internet last week, you probably saw an article, twitter, or Facebook post about the xkcd comic on password strength. The comic, which was (most likely) inspired by an article entitled, “The Usability of Passwords” basically says that using a multi-word password (3 or more words), is more secure than what I have referred to as “complex passwords” in past articles on this blog. The writer of the original article makes the point (which is what the xkcd comic points to) that passwords using three or more dictionary words, has more entropy and is thus harder to crack, therefore making them more secure. While there is a bit of truth to the article, it leads to some false understandings of how hackers actually go about hacking passwords, and make assumptions that aren’t entirely accurate.
Hacking Passwords
The original article explains several methods for hacking passwords. These are, asking, guessing, brute force, common word attacks, and dictionary attacks. You can look at the article to see how the original author describes these methods, but many of them should be self explanatory. Asking and guessing for passwords are what regular non-hacker type people will do. Hackers will also ask for passwords, but they’ll do so in the form of social engineering. Social engineering is basically tricking the person into giving you the password by (most often) pretending to be someone they can trust, like an internal security or IT employee.
The brute force, common work, and dictionary attacks will be performed by hackers, but not necessarily in the manner described by the author.
How the Author Says These Work
The author of “Usability of Passwords” says that these methods are most likely performed at the computer, network, or website that the hacker is attempting to gain access to. And because of this fact the author leads the reader to believe that by allowing only a small number of attempts, followed by a “lock out period” that stops the hacker from logging in for an hour, is enough to keep his password strategy safe.
Before I go further, I want to say that limiting the number of attempts and instituting a lock out period is a good security practice, and should be implemented by large corporations.
How Hackers Really Hack Passwords
The author of “Usability of Passwords” is correct in the fact that hackers will use brute force and dictionary attacks to hack a password. But he’s incorrect in that they are used primarily at the login screens.
Most hackers (at least the good ones) will attempt to acquire the password through social engineering, and then failing that will work on getting the password hash file off a computer. What is a “password hash file” you ask? It’s a file that’s on a computer where the username and the hashed password of the user(s) of the computer is stored. Getting this file is generally a lot of work for the hacker and this is why they’ll usually just attempt to use social engineering.
Once the hacker has the password hash file, they’ll use various programs (I won’t link to them here, you can Google to see what I’m referring to) to then crack the password hashes on their local computers. It is this process where the hacker will use the brute force and dictionary attacks.
The other problem is that some of the dictionary hacking programs can be modified to try combinations of words thus making the idea of using multiple words in a password not nearly as secure as the author would lead you to believe. Is it secure? Not really. Will it take longer for the hacker to crack said password? Yes it will.
The Graphics Card Problem
Another fact that the author ignores (but is mentioned in the article’s comments”, is that graphics cards are incredibly fast. And there are applications available that allow a hacker to utilize their graphics card(s) processor (GPU) to crack password hashes at an alarming rate. More information on this process can be found by reading this article.
What this means is that utilizing brute force and dictionary attacks can be done in even less time.
Why Complex Passwords Are Better
So basically I told you all that to tell you this. Complex passwords are better than using dictionary words. Period.
A complex password is a password that meets following requirements:
At least 8 characters (a minimum of 12 is preferred)
Contains BOTH upper case and lower case letters
Contains numbers
Contains at least 1 special character (examples: !@#$%{^]&*)
Why are these better? Because they can’t be easily figured out with a dictionary attack. They also make brute force attacks more difficult. It’s hard to guess passwords if they have weird characters in them. Long passwords, that meet the other requirements will take years to crack, even when using graphics cards.
The idea is to make it difficult for the hacker to guess, or hack your password, even if they get that password hash. But complex passwords, or multiple word passwords don’t help get around the social engineering problem (the user willfully giving someone their password).
But I Can’t Remember Complex Passwords
The author’s point about using multiple dictionary words, along with the punchline of the xkcd comic, is that such passwords are easier to remember over complex passwords. And while this is an extremely valid point, it defeats the purpose of passwords. Passwords a form of security (some would argue they provide a false sense of security, but that’s a different topic). So passwords should themselves be as secure as possible. This idea of secure passwords comes at the cost of easily being able to remember your passwords, especially since to be really secure you should have a different password for each website that requires one.
This is where “password safes” come into play. Applications like Keepass, LastPass (what I use), and 1Password, allow you to store passwords for individual sites, and they all integrate into your web browser to some degree. All of these applications also have password generators that allow you to create complex, non-dictionary passwords. These generated passwords are then saved with the corresponding site you’ve generated for. What these applications allow you to do is to have a different complex password for each website you visit.
You’re probably asking “how can storing all my passwords in a single place be secure” and it wouldn’t be a bad question. The thing about the applications I’ve listed is they all use high quality encryption to store the passwords and they all require the use of a good “master password” and will warn you when your master password is insecure. You want to have a very secure (around 15-20 characters) complex password as your master password. And you want to make sure that you use that password only for accessing your password safe.
Conclusion
In the end, the author of “Usability of Passwords” makes a convincing case, but not if you know how hackers really operate. His intentions are good though, the idea of using harder to guess/hack passwords is noble regardless of how you say it should be done. But I believe that some of his ideas lead to a false sense of security because of a lack of understanding.
Hopefully, I’ve explained to you why some of the ideas presented in the original article were not so great, and have in turn caused you to think about your passwords, and how to create more secure passwords. I highly recommend that you begin using a password safe, and changing your passwords around the internet to more secure, complex passwords.
