You've read the Anvil(8) man page - is this as good as it gets for spam DDoS protection?
MailChannels Traffic Control provides innovative email traffic shaping solutions for organizations of all sizes, enabling customers to simultaneously solve their spam problems and reduce their email infrastructure costs. On this page, you'll learn how Traffic Control compares with Postfix Anvil, and why you should consider Traffic Control if you are already using or considering using Anvil.
What is Anvil?
Anvil is a light-weight connection rate control mechanism for Postfix, which allows you set limits on how hard someone can hammer your Postfix server. Anvil was created in response to the dramatic up-tick in spam that started happening several years ago, as a way to protect Postfix installations from high connection concurrency and resource exhaustion. It is commonly recommended as the preferred solution to loading issues relating to spam. Anvil is essentially a side-car process that communicates with Postfix to maintain various counters relating to the hosts connected to your Postfix server. Postfix queries anvil to update and retrieve these counters, and take appropriate action to limit the damage from abusive hosts.
What is Traffic Control?
Traffic Control is a highly scalable SMTP proxy server that seamlessly integrates with Postfix. It increases connection capacity so that thousands of concurrent connections can be efficiently prioritized with negligible system load. Legitimate connections are processed right away, known spam is rejected, and suspicious connections are slowed down causing the vast majority of spammers to give up before completing message delivery.
Traffic Control integrates seamlessly with Postfix using the XCLIENT command (see www.postfix.org/XCLIENT_README.html), front-ending SMTP connections, and applying TCP traffic shaping to suspicious connections before passing on legitimate email to Postfix. Traffic Control is implemented using a very efficient libevent-based asynchronous IO layer, which enables handling up to 25,000 concurrent SMTP sessions with low overhead.
Comparison
| Feature | Postfix Anvil | Traffic Control |
|---|---|---|
| Description | Works in conjunction with Postfix to maintain and enforce connection, message, and other rate limits on a per-host basis. | Applies TCP traffic shaping and connection multiplexing, increasing the capacity of Postfix to handle up to 25,000 concurrent connections, while reducing spam by 70-95% more than connection blocking alone. |
| Method of Operation | Receives connection statistics from Postfix, which are maintained in a database and reported back to Postfix via a TCP socket. Postfix enforces rate limits based on the counts reported by Anvil. | Receives SMTP connections, assessing their reputation and behavior through a commercially supported reputation network and set of customizable triggers. Contacts Postfix via SMTP to validate recipients and other SMTP commands in real time, and finally delivers messages to Postfix if the sender adheres to the SMTP protocol and persists long enough to get its message delivered. |
| Effectiveness against botnets | Rate limiting effectively stops high volume senders from abusing Postfix. Protection against botnet-based attacks is minimal, because individual zombies typically "fly under the radar," making only a limited number of connections. | Hits botnets where it hurts, tying up essential SMTP connection resources and causing 70-95% of zombie-based connections to abort before message delivery has taken place. Abusive high volume senders are forced to wait up to 10 minutes for message delivery, greatly reducing the impact of their traffic on Postfix and downstream users. |
| Pricing | Anvil is free - it is part of the open source Postfix package. | Traffic Control is commercial software; however, it is free for low-volume and non-commercial users. Please refer to our download page for details. |
How to find out more
Our Traffic Control blog is an excellent source of commentary on Traffic Control, and the Traffic Control manual explains how it works in much more detail. Of course, you can always download Traffic Control and try it yourself. Or shoot us an email by filling in our inquiry form.
