2 cissp ® Official Study Guide Eighth Edition

Distributed architectures
are prone to vulnerabilities unthinkable in monolithic host/
terminal systems. Desktop systems can contain sensitive information that may be at some 
risk of being exposed and must therefore be protected. Individual users may lack general 
security savvy or awareness, and therefore the underlying architecture has to compensate 
for those deficiencies. Desktop PCs, workstations, and laptops can provide avenues of 
access into critical information systems elsewhere in a distributed environment because 
users require access to networked servers and services to do their jobs. By permitting user 
machines to access a network and its distributed resources, organizations must also recog-
nize that those user machines can become threats if they are misused or compromised. Such 
software and system vulnerabilities and threats must be assessed and addressed properly.
Communications equipment can also provide unwanted points of entry into a dis-
tributed environment. For example, modems attached to a desktop machine that’s also 
attached to an organization’s network can make that network vulnerable to dial-in attacks. 
There is also a risk that wireless adapters on client systems can be used to create open net-
works. Likewise, users who download data from the internet increase the risk of infecting 
their own and other systems with malicious code, Trojan horses, and so forth. Desktops, 
laptops, tablets, mobile phones, and workstations—and associated disks or other storage 
devices—may not be secure from physical intrusion or theft. Finally, when data resides 
only on client machines, it may not be secured with a proper backup (it’s often the case that 
although servers are backed up routinely, the same is not true for client computers).
You should see that the foregoing litany of potential vulnerabilities in distributed 
architectures means that such environments require numerous safeguards to implement 
appropriate security and to ensure that such vulnerabilities are eliminated, mitigated, or 
remedied. Clients must be subjected to policies that impose safeguards on their contents 
and their users’ activities. These include the following:
■
Email must be screened so that it cannot become a vector for infection by malicious 
software; email should also be subject to policies that govern appropriate use and limit 
potential liability.
■
Download/upload policies must be created so that incoming and outgoing data is 
screened and suspect materials blocked.
■
Systems must be subject to robust access controls, which may include multifactor 
authentication and/or biometrics to restrict access to end-user devices and to prevent 
unauthorized access to servers and services.
■
Restricted user-interface mechanisms and database management systems should be 
installed, and their use required, to restrict and manage access to critical information 
so users have minimal but necessary access to sensitive resources.
■
File encryption may be appropriate for files and data stored on client machines (indeed, 
drive-level encryption is a good idea for laptops and other mobile computing gear that 
is subject to loss or theft outside an organization’s premises).

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352
Chapter 9 
■
Security Vulnerabilities, Threats, and Countermeasures
■
It’s essential to separate and isolate processes that run in user and supervisory modes 
so that unauthorized and unwanted access to high-privilege processes and capabilities 
is prevented.
■
Protection domains should be created so that compromise of a client won’t automati-
cally compromise an entire network.
■
Disks and other sensitive materials should be clearly labeled as to their security classi-
fication or organizational sensitivity; procedural processes and system controls should 
combine to help protect sensitive materials from unwanted or unauthorized access.
■
Files on desktop machines should be backed up, as well as files on servers—ideally, 
using some form of centralized backup utility that works with client agent software to 
identify and capture files from clients stored in a secure backup storage archive.
■
Desktop users need regular security awareness training to maintain proper security 
awareness; they also need to be notified about potential threats and instructed on how 
to deal with them appropriately.
■
Desktop computers and their storage media require protection against environmental 
hazards (temperature, humidity, power loss/fluctuation, and so forth).
■
Desktop computers should be included in disaster recovery and business continuity 
planning because they’re potentially as important as (if not more important than) other 
systems and services within an organization for [or in] getting their users back to work 
on other systems.
■
Developers of custom software built in and for distributed environments also need 
to take security into account, including using formal methods for development and 
deployment, such as code libraries, change control mechanisms, configuration manage-
ment, and patch and update deployment.
In general, safeguarding distributed environments means understanding the vulnerabili-
ties to which they’re subject and applying appropriate safeguards. These can (and do) range 
from technology solutions and controls to policies and procedures that manage risk and 
seek to limit or avoid losses, damage, unwanted disclosure, and so on.
A reasonable understanding of countermeasure principles is always important when 
responding to vulnerabilities and threats. Some specific countermeasure principles are dis-
cussed in Chapter 2, “Personnel Security and Risk Management Concepts,” in the section 
“Risk Management.” But a common general principle is that of defense in depth. 
Defense 
in depth
is a common security strategy used to provide a protective multilayer barrier 
against various forms of attack. It’s reasonable to assume that there is greater difficulty in 
passing bad traffic or data through a network heavily fortified by a firewall, an IDS, and a 
diligent administration staff than one with a firewall alone. Why shouldn’t you double up 
your defenses? Defense in depth (aka 
multilayered defense
and 
diversity of defense
) is the 
use of multiple types of access controls in literal or theoretical concentric circles. This form 
of layered security helps an organization avoid a 
monolithic security stance
. A monolithic 
or 
fortress mentality
is the belief that a single security mechanism is all that is required to 
provide sufficient security. Unfortunately, every individual security mechanism has a flaw 

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Distributed Systems and Endpoint Security 
353
or a workaround just waiting to be discovered and abused by a hacker. Only through the 
intelligent combination of countermeasures is a defense constructed that will resist signifi-
cant and persistent attempts of compromise.