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CompTIA A+ Certification All-in-One Exam Guide

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MAC Address Filtering

It’s far from bulletproof, but if an attacker does gain physical access to your

site, you may be able to throw up another hurdle to limit their ability to

access your network with any of their own devices. Both wired and wireless

networks can use MAC filtering or port security to enable you to blacklist or

whitelist devices based on their MAC address.

Use a blacklist to block specific computers, adding their MAC addresses

to the ranks of the undesired. You can use a whitelist to pre-specify the only

MAC addresses allowed access. I say this isn’t bulletproof because a savvy

attacker can spoof an address (they’ll have a much easier time sniffing a valid

Wi-Fi MAC address than a wired one, though) from another device accessing

the network.

Keeping devices you don’t control out of your network is a big win! If the

attacker can’t gain access to your network with one of their own devices

(which they have probably preloaded with tools for attacking your systems or

network), they’ll have to resort to breaking into one of your devices to do the

heavy lifting.

Authentication

Security requires properly implemented authentication, which means in

essence how the computer determines who can or should access it and, once

accessed, what that user can do. A computer can authenticate users through

software or hardware, or a combination of both.

You can categorize ways to authenticate into three broad areas: knowledge

factors, ownership factors, and inherence factors. You read about multifactor

authentication in detail in Chapter 25, “Care and Feeding of Mobile

Devices,” when talking about mobile device security. It works the same way

when securing a desktop computer, a laptop, a server, or a building. There’s

no reason to rehash it here. The only thing to add is that many organizations

use two-factor authentication. An example is a key fob that generates a

numeric key. A user authenticates by entering his or her user name and

password (something the user knows) and enters the key (something the user

has) when prompted.

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