network-based intrusion detection

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NETWORK-BASED INTRUSIONDETECTION

FORESEC Academy Security Essentials (III)

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Need for Network-basedIntrusion Detection

Most attacks come from the Internet Detecting these attacks allows a site to

tune defenses If we correlate data from a large

number of sources we increase ourcapability

The statistic that 90% of all attacks are perpetrated by

insiders is dead wrong.

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Inside a Network Attack

WinNuke, (also called OOBNuke), uses TCP 139 and OOB Data, even if NetBIOS is not enabled. It results in the “Blue Screen of Death”.

Patches/service packs are available

OOB stands for Out Of Band and is actually misnamed;it should say .Urgent mode., which is Urgent bit set inthe TCP header flags and the urgent pointer.

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Nuke’eM Screen

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BlackIce – Nuke ‘Em Detection

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Network IntrusionDetection 101

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BlackIce - Enable Logging

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BlackIce - Viewing Logs

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BlackIce - Visualization Tools

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Libpcap-based Systems

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Network Intrusion DetectionWith Snort

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Snort Design Goals

Low cost, lightweight Suitable for monitoring multiple

sites/sensors Low false alarm rate Efficient detect system Low effort for reporting

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Snort

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Writing Snort Rules

Can create custom rules to filter on specific content.

Pre-loaded with hundreds of rules (but you may need to create one or more custom

rules) Simple to write yet powerful enough to

capture most types of traffic Options

- Basic (Pass, Log, Alert) - Advanced (Activate, Dynamic)

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