Intrusion
Detection Systems (IDS) vs Intrusion Prevention Systems (IPS): What’s What?
An Intrusion Detection System (IDS) and
Intrusion Prevention System (IPS) have very similar acronyms by which they are
commonly known, yet they perform very different tasks within the network
security process. So what exactly do they do, how do they do it, and does your
organization need either, neither, or both as part of your overall security
posture?
Intrusion
Detection System
Definitions are important in the security
world—you have to understand what you are dealing with before you can
accurately determine if it's a good fit for the needs of your organization. So
what exactly is an Intrusion Detection System (IDS)? Simply put, an IDS can be
either a hardware device or software application that monitors network traffic,
incoming and outbound, for any malicious activity or security policy violation.
Think of it as an intruder alarm, sounding an alert if it spots any activity
that could lead to network and data compromise. It does this by inspecting the
packets that flow across the network in order to detect known indicators of
compromise and traffic patterns that suggest suspicious activity. In other
words, an IDS is a passive system used to bring real-time visibility into
potential network compromises.
How the IDS
achieves this will depend on the type of system being deployed. They can be
either network based, or host based. Network-based Intrusion Detection Systems
(NIDS) will have sensors strategically placed within the network itself,
sometimes at multiple locations, to monitor the most traffic without creating
performance bottlenecks. Host-based Intrusion Detection Systems (HIDS) do
things differently, and are run on specific hosts or devices, only monitoring
the traffic associated with them. Either type can take different approaches to
detecting suspicious traffic. Some might use signature detection, comparing
packets against a database of known threats. Some might use an anomaly-based
approach, comparing traffic patterns against an established network “normality”
baseline. Some will combine both methods. All are known for generating false
positives, at least initially. The IDS will need configuration to fine-tune it
for the particular “norms” of your network and the devices attached to it.
Intrusion
Prevention System
An Intrusion Prevention System
(IPS) is like an IDS on steroids. Not only can it detect the same
kind of malicious activity and policy violation that an IDS does, but as the
name suggests it can execute a real-time response to stop an immediate threat
to your network. Like an IDS, the IPS can be NIPS-based with sensors at various
points of the network or HIPS-based with sensors on the host to monitor
individual devices. Unlike the IDS, an IPS has the ability to configure
policy-based rules and actions to be executed when any anomaly is detected.
Think of it as being an active defense system, tailored to best suit your
business needs in terms of security posture.
Although often considered a
firewall, this is an erroneous assumption about an IPS. If anything, an IPS is
a firewall in reverse: The firewall applies a rule-set to allow traffic to
flow; an IPS applies a rule-set to deny and drop traffic. That said, there are
Unified Threat Management (UTM) devices, which do both and therefore act as
firewall and IPS simultaneously. These might appear to offer the best of both
worlds, in that they can actively allow “good” traffic while also blocking
known “bad” traffic. However, UTMs can be hard to manage optimally, and
tend not to enable the same granularity of control over IPS protections as a
stand-alone IPS can offer.
Which
do you need?
Now you know the differences
between an IDS and IPS, which does your organization need as part of its
network security implementation? Truth be told, the stand-alone IDS has pretty
much been replaced by the IPS as far as the IT security industry is concerned.
That's not to say intrusion detection is a busted flush, but rather that detection
has to be accompanied by prevention technologies in today’s increasingly
frantic threat climate. For most organizations, the notion of administering an
IDS as a separate solution alongside other reactive solutions makes little
sense. What makes more sense is to adopt a layered approach to detection and
prevention while working with a managed service provider (MSP) able to make
better sense of the complexities of the security function and respond to alerts
more effectively.
