CompTIA A+ Certification All-in-One Exam Guide

something the user either is or something they do. An example of an
inherence factor is a biometric identifier, such as a fingerprint or retinal
pattern. You commonly hear these three factors referred to as something the
user knows, something the user has, and something the user is.
Other authentication factors exist, but are not as commonly considered in
security authentication. For example, there’s the location factor: somewhere
you are. This can be used if the individual’s location can be pinpointed via
GPS or some other method. The individual may be required to be at a certain
location in order to log in to the system, for example. Yet another is the
temporal factor. As the name implies, schemes using the temporal factor may
require logon at a certain time of day, or even within so many seconds or
minutes of another event. Token methods of authentication also use time
factors, as the PIN displayed on a token is only good for a finite amount of
time.
Armed with the factors, let’s consider authenticating with a single factor.
The most common schemes require a user name and password; both are
something you know, so the scheme uses a single factor. You can also think
of a traditional door lock as single-factor authentication; the key it requires is
something the user has—a possession factor.
During the initial push to move beyond single-factor authentication, the
term two-factor authentication grew common—and you’ll still hear people
use this term. Over the years, however, authentication methods using more
than two factors have grown increasingly common, so it has become more
correct to say multifactor authentication. Multifactor authentication can use a
variety of methods, as long as it uses more than one.
Just because the term sounds fancy and might make us think of complex
systems at secret government installations, don’t assume multifactor
authentication hasn’t played a role in everyday life for decades. For example,
when you use a bank’s ATM, you’re using multifactor authentication:
something you possess (the ATM card) and something you know (the correct
PIN).
EXAM TIP Don’t confuse the user name and password combination with