Change your password four times a minute!

A Swiss researcher has developed a way to crack Windows passwords in an average of 13.6 seconds according to this: http://news.com.com/2100-1009_3-5053063.html?tag=fd_top

A quote from the article:

The result: The same password encoded on two Windows machines will always be the same. That means that a password cracker can create a large lookup table and break passwords on any Windows computer. Unix, Linux and the Mac OS X, however, add a 12-bit salt to the calculation, making any brute force attempt to break the encryption take 4,096 times longer or require 4,096 times more memory.

Well, that is 15 hours, which is a bit long, but keep in mind that the very first thing someone needs is your encrypted passwords. Although this article doesn't point this out, on Unix and modern versions of Windows, you can't get those without root or administrative access. It is unfortunately true that Windows has suffered from a lot of security flaws that can be used to gain such access fairly easily, but Unix hasn't been immune to that either.

I offer a simple solution for this. Unix users need to change their passwords twice a day, and their Windows brethren should do so four times each minute.

Seriously, my experience it that people don't understand the need for strong passwords nor what a good password is. Just the other day I set up a user for ssh access to the corporate system and, after explaining that we couldn't use the "same as your login " scheme that was used inside the building, asked her for a password. With a conspiratorial flair, she turned away and wrote something on a small piece of paper, which she then carefully cupped in her hand to show to me. It said: ALPHA

That's not a good password. It's not even close. A good password needs mixed upper and lower case, numbers, and punctuation. Passwords like "ALPHA" don't need root or administrative access: they can be guessed with simple dictionary attacks.

One way to make up passwords that are both good but easy to remember is to use a phrase you can remember (perhaps from a song or a poem) and get creative with it. For example, "There must be 50 ways to save money!" becomes "Tmb50!w27m" ("seven" for "save" and moving the exclamation after 50), and "I just hate to forget MY password!" is "Ijh824gM!p".

Finally, although it is very tempting to use the same password everywhere, don't. A trick I use is to have a very long, phrase generated password. The phrase I use falls very naturally into two parts, which gives me quite a few easy to remember passwords:

• The first part
• The second
• First followed by second
• Second followed by first
• First backwards
• Second backwards
• First followed by second backwards
• Second followed by first backwards
• First and second, all backwards
• Second and first, all backwards.
• All of the above with 2-3 leading or trailing extra punctuation characters.

While I may not instantly remember which I used at a given place, I can usually get it within a few tries. But if someone should get hold of one of my passwords, they aren't going to have instant or easy access to everywhere else.

Since writing this, I came up with a better way to generate unique but easily remembered passwords. See it at Easy to remember unique passwords.
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11 comments

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Sun May 16 01:53:24 2010:   anonymous


pls help me i lost my password root server linux





Sun May 16 02:02:26 2010:   TonyLawrence


See http://aplawrence.com/Linux/lostlinuxpassword.html



Thu Jun 24 13:22:00 2010:   TonyLawrence


I recently came up with an even better way to do this:

http://hubpages.com/hub/Easy-to-remember-unique-passwords



Tue Jul 6 12:45:49 2010:   anonymous


hello guys i'm shocked realy it's a nice website and very helpful but i need help in somethin and i'm sure u could help me with it.. i need to backdoor my root but by an email , what i mean is that when someone get into my box and change it automaticly sends me a msg into my email with the new passwd that the hacker put it . note: please in the simplest way cause i'm new on linux thank u i hope u help me fast



Tue Jul 6 13:10:42 2010:   TonyLawrence


Unlikely to be of value. Most of these things are escalations, no need for them to change a password.



Tue Jul 6 13:14:27 2010:   anonymous


hmmmm but if he brakes into my system and change it how should i reaccess my box that will be impossible :/



Tue Jul 6 13:20:44 2010:   TonyLawrence


If someone hacked your box, the password is the least of your problems.

However, if you had read other folks comments and answers, you would know the answer to that already.

By the way, a real hack is unlikely to want to alert you by doing something so obvious as changing your password.



Tue Jul 6 13:26:52 2010:   anonymous


i red but i'm realy 0 in linux like i don't know nothin just few things like nano and cat /proc/cpuinfo those things but i realy don't know what u r talkin about now cause if password is my least problem then should i keep it root:root =)) btw i don't have linux windows cause i don't know how to config it but i'm still tryin to find out how to config from google and these websites like the one of urs but i would like to help me with the 1st post backdooring my root with and email address thank u



Tue Jul 6 14:21:08 2010:   TonyLawrence


Probably the most useful advice comes from http://serverfault.com/questions/51883/how-can-you-prevent-root-password-change-on-linux



You could use PAM (Pluggable Authentication Modules) to allow you to log in as root, regardless of what they set the password to. There are a lot of modules available, so I'll just leave this one hanging.

You create 'a second root user' by opening /etc/passwd and adding a new user with the same UID as root (0). Then add a password into the /etc/shadow file for that specific user. This will allow you to log in as root and even if they change the password for 'root' - your login still works.

Create a shellscript that is run periodically to check if the hash of the root user in /etc/shadow for root matches the one you want it to be. If it's not, the hash is changed back.

As others have pointed out, giving root access will allow them to do absolutely what ever they like on the system and if they really want to lock you out; they can. The options above however make it harder or less transparent to them.




Tue Jul 6 18:19:50 2010:   anonymous


hello thanks tony u r realy awosm and i found something better from the website u gave me chattr +i /etc/shadow this one is good thank u agian



Tue Jul 6 20:03:17 2010:   TonyLawrence


Sigh.

But as I said, if you are hacked, it is likely to be through an escalation and the LAST thing the hacker would want to do is change the password.

That chattr will prevent ALL password changes, which is at the least an inconvenience and again unimportant to a real attack.

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