Networks

Mandatory Firewall Rules for Internet Facing Firewalls

1. Introduction

In a past life I worked for a large company, first as a network firewall administrator and eventually made my into the security team as a network security specialist, responsible for developing and auditing the network security standards. While I wrote many network related standards and best-practices documents, the following was definitely one of my favorites. I had to convert and sanitize the content and while it is very lengthy (and not suitable for a blog), I figured I give it a shot at posting to my site.

A special thanks to Yuri Kopylovski who helped me co-author this guide and to the many folks at www.anti-online.com who benefited from the content over the years. This was originally published in 2007 under my alias “aciscorouter” and has since been edited to include suggestions from the Anti-Online community.

You will note that the rule order is identified in the first column I provide with the samples under all descriptions (i.e. the very first rule is a drop rule against the firewall and the very last should be a “clean-up” rule).

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Basic Log Storage Calculations

Determining the sizes of log management systems requires knowledge of the number of devices being monitored and the anticipated event rates for each class of system. In many customer engagements, Professional Services time may be required to measure the event rate calculations from all of the monitored devices. This is important since there are too many variables to predict the average or peak Events Per Day (EPS) of any given system. I would caution any customer that if the vendor they are working with gives them “magic” calculations and pricing without gathering the necessary information regarding customer-specific speeds and feeds, they can expect to spend a lot more money later once the vendor gets their foot in the door. Basically, poor planning will result in unavoidable OP/EX costs later.

EPS is one metric used by many log management and SIEM vendors to determine such factors as licensing, storage and peak system loads. Another variable used could be Events Per Day (EPD), especially when it relates to storage sizing and license enforcement. This is why it’s imperative that accurate device counts and product types are audited when planning a centralized log management or SIEM solution.

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