1. Computing

Host-Based Intrusion Prevention

Things To Look For In This Last Line of Defense

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Layered security is a widely accepted principle of computer and network security (see In Depth Security). The basic premise is that it takes multiple layers of defense to protect against the wide variety of attacks and threats. Not only can one product or technique not protect against every possible threat, therefore requiring different products for different threats, but having multiple lines of defense will hopefully allow one product to catch things that may have slipped past the outer defenses.

There are plenty of applications and devices you can use for the different layers- antivirus software, firewalls, IDS (Intrusion Detection Systems) and more. Each has a slightly different function and protects from a different set of attacks in a different way.

One of the newer technologies is the IPS- Intrusion Prevention System. An IPS is somewhat like combining an IDS with a firewall. A typical IDS will log or alert you to suspicious traffic, but the response is left to you. An IPS has policies and rules that it compares network traffic to. If any traffic violates the policies and rules the IPS can be configured to respond rather than simply alerting you. Typical responses might be to block all traffic from the source IP address or to block incoming traffic on that port to proactively protect the computer or network.

There are network-based intrusion prevention systems (NIPS) and there are host-based intrusion prevention systems (HIPS). While it can be more expensive to implement HIPS- especially in a large, enterprise environment, I recommend host-based security wherever possible. Stopping intrusions and infections at the individual workstation level can be much more effective at blocking, or at least containing, threats. With that in mind, here is a list of things to look for in a HIPS solution for your network:

  • Doesn't Rely On Signatures: Signatures- or unique characteristics of known threats- are one of the primary means used by software like antivirus and intrusion detection (IDS).The downfall of signatures is that they are reactive. A signature can't be developed until after a threat exists and you could potentially get attacked before the signature is created. Your HIPS solution should use signature-based detection along with anomaly-based detection which establishes a baseline of what "normal" network activity looks like on your machine and will respond to any traffic that appears unusual. For example, if your computer never uses FTP and suddenly some threat tries to open an FTP connection from your computer, the HIPS would detect this as anomalous activity.

  • Works With Your Configuration: Some HIPS solutions may be restrictive in terms of what programs or processes they are able to monitor and protect. You should try to find a HIPS that is capable of handling commercial packages off the shelf as well as any home-grown custom applications you may be using. If you don't use custom applications or don't consider this a significant problem for your environment, at least ensure that your HIPS solution protects the programs and processes you do run.

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