So
what's the big deal? Well, think about it this way. You have
a workstation at home and a workstation at work. You have bank
accounts, e-mail accounts, and so on. It adds up. Now imagine
you work in the IT field. It's conceivable to have 50 or more
passwords to memorize. What if you had to change these passwords
each month? Not only would you have a dozen (or possibly a few
dozen) passwords to remember, but you would need to change them
and remember the new passwords immediately.
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One
of the great obstacles to effective password creation is laziness.
We all want to have something easy to remember so we tend
not to be very careful or creative in devising passwords.
Then you have to take into account a company's policy on password
security. Most companies have a policy in place that forces
all users to create a new and unique password each month.
What winds up happening is that end users simply add a numerical
digit to the end of their last password. If the password is
"dog", then the new password becomes "dog1", eventually growing
to "dog11". This sort of password creation technique is insecure
and it doesn't help matters when an end user writes their
password on a sticky note and places it under their keyboard
or right on their monitor.
Many
users believe that their desk drawers are sufficiently secure
for hiding passwords. Another common place for storing passwords
is on a PDA, which would be fine if PDAs were never lost or
stolen. There are in fact security solutions for PDAs, such
as PDA Secure, a program that adds protection to your PDA
via encryption (see Resources for
a link). But the best advice is to avoid storing passwords
on your PDA or obvious places such as desk drawers altogether.
As
a security analyst, I am regularly asked for my advice on
creating an effective password scheme while maintaining the
integrity for multiple platforms. In the next few sections,
I hope to provide some useful ideas.
Ineffective passwords
The most important thing to remember is that any password
you create is vulnerable to attack, which is called password
stealing or cracking. This is the exploitation of your credentials
via unauthorized access. The article Introduction to password
cracking (see Resources) provides
details on password cracking techniques.
The
first step in good password design is to look at what not
to do when creating passwords. First off, avoid dictionary
words. Any word that comes from the dictionary is susceptible
to an attack and eventually will be cracked unless you change
it often. The major problem with creating passwords from dictionary
words is that any password-cracking tool can eventually guess
it using a dictionary attack. Also, you never want to write
a dictionary word backwards or add a simple numerical value
after the dictionary word. These same password-cracking tools
try these combinations as well. Here are some examples of
bad passwords:
These
are all very susceptible to exploitation. Here are a few other
things to avoid when creating a password:
- Never
use personal information as the basis of a password. If
you are a Star Trek fan, for example, don't set all your
passwords to "Spock", "Vulcan", or even "Spock1". These
are easily guessed by anyone who knows you.
- Sports
fans just can't help themselves. I have known several administrators
who have used their favorite team or player as the basis
for a password.
- Don't
use passwords based on what you keep on your desk. I hacked
into a client's server using his daughter's name after seeing
a picture of her on his desk.
- Don't
keep password files on your local machine or a network share.
This is only secured via file level access, while the machine
itself can be compromised. And if someone resets permissions
on a folder and does it incorrectly, the folders underneath
are also reset, compromising all passwords on the network.
How to create good passwords
Here are some general rules for creating effective passwords:
- The
only safe place to keep a password is in your head or a
locked safe, which only you know the combination to.
- Effective
passwords need to be fairly long, but not so long that you
can't remember them. Three-character passwords are too short.
- Use
special characters, uppercase letters, and numerals in a
logical manner. Here are some examples:
- Uppercase
letters: Using uppercase letters in conjunction with
lowercase letters will offer some protection if you have
the functionality of "case sensitivity." You could then
use the password "HeyYou", which is different from "heyyou".
Adding uppercase letters adds a layer of complexity making
passwords harder to crack.
- Special
characters: Using special characters such as "#",
or "%" also adds to complexity. Take the word "money",
add the pound sign after it (money#) and you have a fairly
effective password.
- Numerals:
Using numerals also adds complexity to the mix. If your
social security number is 123-45-6789, you can use the
last four digits with an easily remembered word such as
"money", making your password "money6789".
- Mnemonic
phrases: If you're a phrase collector from movies
or songs, you can take a great line and make it into a
password. Let's say you're a Star Wars fan. You can take
the phrase: "May the Force Be With You" and use the first
character from each word to create the password "MTFBWY".
- Substitution:
You can use a number or sign in substitution for a word.
If you know that the "$" sign equals the word "money,"
then you can tie it into a password scheme such as "Ilove$".
This is simple-to-remember password that is difficult
to crack.
Next,
we'll tackle the problem of creating effective password schemes
for multiple systems.
Creating a password scheme that works
In this section we look at password schemes for personal, home-based
machines, work-related systems and networks, and a password
scheme specifically for Cisco routers and switches not employing
the CiscoSecure-based Tacacs+. CiscoSecure is a product that
uses the Tacacs+ protocol to allow routers and switches to have
login authentication performed by an external source like a
UNIX server instead of the typical login passwords kept on the
devices themselves.
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Personal home-based PCs
An effective password scheme on home-based personal PCs uses
a combination of the above theories. You'll want to make it
fairly easy to remember because once you forget it, you'll
have a problem getting into your machine without the skill
set to break back in. You also need to consider the following:
- If
you are running the Windows 9X platform, you don't need
to worry about a password because passwords mean nothing
to the security of the local machine. Your password is based
on a profile, and if you press Cancel, you will bypass the
machine's login. Also, a password-protected screensaver
can be eliminated by rebooting the machine.
- If
you are running the Windows NT, 2000, or XP platform, you
want to make sure that you do not forget your passwords.
You need to make sure you have the Administrator account
locked down with a good password and that it is well hidden
so that your machine won't be compromised. However, if you
forget it, you want a way to get back in. This is accomplished
by making a new account and password protecting it so you
have a back door.
Home-based
security is quite different from corporate security, so the
guidelines are based on a person's level of comfort and paranoia.
Here is an example of a password scheme for home use that
is easy to remember: Use a mix of a pet names, upper and lowercase
letters, with the last four digits of your social security
number and a special character. The password you create might
look like: Butch#8976
This
example can also be used for Web sites, bank accounts, and
other personal use systems. This type of password is virtually
impossible to crack and is easy to remember.
Network administrator systems
What if you're in the unenviable position of a network administrator?
Well, that's a little more difficult because you will be responsible
for the passwords of many systems.
Password
protection follows the same rules as before just on a wider
scale. You will most likely have numerous systems to secure
with passwords and what's more, you may even have levels
of passwords depending on what type of access you want to
grant users. In other words, you can have a Cisco router with
multiple levels of login access, with each level giving more
privileges.
You
can use the same theories as listed in the first section of
this article (uppercase, special characters, etc.) but with
a new twist. Instead of picking a great name to remember,
or a single word, you need to come up with a theme. Note:
DO NOT use my example. It has been done before.
One
of my favorite movies of all time is "Reservoir Dogs." In
this movie, all the bad guys are given names based on colors:
Mr. Black, Mr. White, and Mr. Pink. This theme can be tied
into a password scheme for your network servers. Here is what
it might look like:
| Server
name |
Server
type |
Password |
| MNN-DC-1 |
Domain
controller |
Pink$DC1 |
| MNN-DC-2 |
Domain
controller |
White$DC2 |
| MNN-DNS-1 |
DNS
server |
Black$DNS1 |
| MNN-DNS-2 |
DNS
server |
Red$DNS2 |
| MNN-DHCP-1 |
DHCP
server |
Green$DHCP1 |
| MNN-WINS-1 |
WINS
server |
Orange$WINS1 |
| MNN-FS-1 |
File
server |
Yellow$FS1 |
Notice
that each server has a password that includes the color and
a special character (the same among them all) along with part
of the server name. Also, notice the upper and lower case
letter usage. The likelihood of these passwords being cracked
is extremely slim. This is an example of a solid password
scheme; it works and it is something you can remember with
little effort. Again, you can (and should) customize this
to your needs.
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Cisco administrator password schemes
The table below shows an effective password scheme for Cisco
routers. Cisco routers require two levels of passwords: an
initial password and an enable secret password.
| Password |
Enable
secret |
| DoNot$ |
$HackMe |
| DoNot$ |
$PingMe |
| DoNot$ |
$CrackMe |
| DoNot$ |
$SpoofMe |
Because
Cisco routers accept case-sensitive passwords, you have a
nice upper and lower case pattern here, special characters,
and an easy-to-remember phrase.
For
Cisco, you need an initial password to log into the router
and a second level for more secure access, which you can configure
as the enable secret password. This chart gives you an idea
on how to configure this option. By making the password scheme
relate to something you enjoy, such as a movie, you are more
likely to remember it (not all security-related work needs
to be a drag!); but more importantly -- make sure it's secure.
Summary
Passwords are a necessary, though inconvenient, part of our
lives. All systems need them to have a simple-to-implement
first level of access security. The question for IT professionals
and users of all levels is how do we work with them and not
go out of our minds? In this article we demonstrated how to
effectively create individual passwords and password schemes.
Passwords and password schemes need to be difficult to crack
and easy to remember. Because passwords are a pain to remember
and keep track of, people tend to put little effort into creating
them, thus compromising their own security and the security
of others. It's important to keep in mind, however, that no
matter how effective the password or password scheme, there
is always a level of risk associated with passwords.
Resources
About the author
| Robert
J. Shimonski has numerous certifications and is a
Lead Network and Security Engineer for a major manufacturing
company. Robert's specialties include network infrastructure
design, security design, and network management and troubleshooting
using many products including firewalls and multiple Cisco
products. Robert is the author of many security-related
articles and published books, including the Sniffer Network
Optimization and Troubleshooting Handbook and the upcoming
Security+
Study Guide and DVD Training System both from Syngress
Media, Inc. Read more about Robert at his site, http://rsnetworks.net,
and be sure to check out his book on using Network Associates’
Sniffer Solutions suite of tools: Sniffer Pro Network
Optimization & Troubleshooting Handbook.
|
 |
Reprinted with permission from the author. Originally appeared
at IBM
developerWorks.