Beating Spam and Viruses with amavisd-new and Maia Mailguard
Most spam filters are concerned only with defending against the onslaught of spam and do little or nothing to prevent it in the first place. Because Maia allows users to confirm the status of their mail as spam and does nothing to modify the original mail headers, this spam can be reported in a number of different ways. Upcoming versions of Maia will support detailed header analysis and semi-automated reporting to ISPs. These reports help others block spam more effectively and even can result in some form of punishment for the spammer.
Behind the scenes, Maia's automated scripts process the quarantine at regular intervals, reporting confirmed spam to the same collaborative networks that SpamAssassin consults—Vipul's Razor, Pyzor and the DCC. By sharing this information with these networks, you give something back, rather than only benefiting from the reports of others.
In the end, what matters most is how effective the combination of amavisd-new and Maia Mailguard is at keeping spam out of your inbox, while keeping ham out of your quarantine. From my own site's statistics, that figure is a refreshing 99.22%, with 0.26% false positives and 0.52% false negatives. Best of all, those false positives can be recovered easily from the quarantine and the false negatives can be reported from the ham cache.
For viruses and other forms of malware, the effectiveness figure is even more impressive: 100%. In the six months since I installed this content-filtering solution, the virus scanners on my desktop machines haven't caught anything that slipped past the filters. This is largely due to the way amavisd-new allows multiple virus scanners from different vendors to be used together—what one scanner misses, another typically catches.
Performance-wise, any content-filtering solution is going to slow down mail processing to some extent. It often becomes a trade-off between filter effectiveness and speed, as you may choose to disable certain filters and tests to improve mail throughput. My 99.22% effectiveness statistic comes from having every available test and filter enabled, for example, but it also costs 1–3 seconds to process each mail item on a moderately loaded dual-PIII 733MHz with 1GB of RAM. A busier site might not be able to tolerate that kind of delay. They would have to choose between disabling the more time-consuming tests, upgrading the processor and RAM in the content filter and switching to a load-balanced array of content filters. Nevertheless, Maia Mailguard and amavisd-new are being used together at sites hosting more than 50,000 users, processing more than 350,000 e-mails a day, so the solution scales if you've got the hardware to handle it.
As many people already have discovered, some of the best weapons in the war against spam and viruses happen to be open-source tools. With tools like amavisd-new, Maia Mailguard, SpamAssassin and Clam Antivirus, you can provide your network with world-class protection without spending tens of thousands of dollars.
Resources for this article: www.linuxjournal.com/article/7820.
Robert LeBlanc is the president of Renaissoft (www.renaissoft.com), author of Maia Mailguard and resident spam-fighting guru for the AnswerSquad (www.answersquad.com). When he's not reinventing the wheel or building better mousetraps, he can be found in the company of his four Alaskan Klee Kai, Zorro, Sikari, Piyomi and, of course, Maia.
Fast/Flexible Linux OS Recovery
On Demand Now
In this live one-hour webinar, learn how to enhance your existing backup strategies for complete disaster recovery preparedness using Storix System Backup Administrator (SBAdmin), a highly flexible full-system recovery solution for UNIX and Linux systems.
Join Linux Journal's Shawn Powers and David Huffman, President/CEO, Storix, Inc.
Free to Linux Journal readers.Register Now!
- Back to Backups
- Download "Linux Management with Red Hat Satellite: Measuring Business Impact and ROI"
- A New Version of Rust Hits the Streets
- Google's Abacus Project: It's All about Trust
- Secure Desktops with Qubes: Introduction
- Seeing Red and Getting Sleep
- Fancy Tricks for Changing Numeric Base
- Secure Desktops with Qubes: Installation
- Working with Command Arguments
- CentOS 6.8 Released
Until recently, IBM’s Power Platform was looked upon as being the system that hosted IBM’s flavor of UNIX and proprietary operating system called IBM i. These servers often are found in medium-size businesses running ERP, CRM and financials for on-premise customers. By enabling the Power platform to run the Linux OS, IBM now has positioned Power to be the platform of choice for those already running Linux that are facing scalability issues, especially customers looking at analytics, big data or cloud computing.
￼Running Linux on IBM’s Power hardware offers some obvious benefits, including improved processing speed and memory bandwidth, inherent security, and simpler deployment and management. But if you look beyond the impressive architecture, you’ll also find an open ecosystem that has given rise to a strong, innovative community, as well as an inventory of system and network management applications that really help leverage the benefits offered by running Linux on Power.Get the Guide