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Transparent outbound filtering: An upcoming series of blog posts

By Ken Simpson | 1 minute read

Over the next few months, we are going to be writing a series of posts about filtering outbound spam as it exits (or attempts to exit) an ISP’s network. This series of posts will be tracking our actual efforts as we work with a mid-sized ISP (~1M users) to help them prevent botnet-originated spam from leaving their subscriber network by forcing port 25 traffic to pass through an intermediate filtering layer running Traffic Control.

To pique your interest in the upcoming posts, you may be interested to know that we will be implementing Traffic Control 4.x in a fully transparent configuration – intercepting all of the ISP’s outbound port 25 traffic, scanning it for spam using an efficient filter, applying some traffic shaping and blocking, and then forwarding it to the destination mail server. We’ll be talking about how we can proxy SMTP AUTH requests, and how SSL (i.e. STARTTLS) can be accommodated in such a situation without adversely affecting users.

Questions before we get started? Just leave us a comment.

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