Section: Threats and Vulnerabilities
Explanation/Reference:
Explanation:
Most intrusion detection systems (IDS) are what is known as signature-based. This means that they
operate in much the same way as a virus scanner, by searching for a known identity - or signature - for
each specific intrusion event. And, while signature-based IDS is very efficient at sniffing out known
methods of attack, it does, like anti-virus software, depend on receiving regular signature updates, to keep
in touch with variations in hacker technique. In other words, signature-based IDS is only as good as its
database of stored signatures.
Any organization wanting to implement a more thorough - and hence safer - solution, should consider what
we call anomaly-based IDS. By its nature, anomaly-based IDS is a rather more complex creature. In
network traffic terms, it captures all the headers of the IP packets running towards the network. From this,
it filters out all known and legal traffic, including web traffic to the organization's web server, mail traffic to
and from its mail server, outgoing web traffic from company employees and DNS traffic to and from its
DNS server.
There are other equally obvious advantages to using anomaly-based IDS. For example, because it detects
any traffic that is new or unusual, the anomaly method is particularly good at identifying sweeps and
probes towards network hardware. It can, therefore, give early warnings of potential intrusions, because
probes and scans are the predecessors of all attacks. And this applies equally to any new service installed
on any item of hardware - for example, Telnet deployed on a network router for maintenance purposes and
forgotten about when the maintenance was finished. This makes anomaly-based IDS perfect for detecting
anything from port anomalies and web anomalies to mis-formed attacks, where the URL is deliberately
mis-typed.