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Resume/CV: Justin Mason

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Senior software engineer with a strong devops skill-set, and experience in leading the design, development and operation of large-scale software projects. These range from Apache SpamAssassin, the world-leading open-source spam filter, to a world-wide network monitoring system used internally within Amazon.


Specialities: Linux, open source, anti-spam, mail, internet security, mail filtering, scalability

Programming languages, libraries and frameworks:

Standards and protocols:

Internet-oriented software development:

Systems administration, ops, and infrastructure:

Development methodologies:


SDE, (Dublin, Ireland) (Jul 2009 - present):

Developing products and services to perform Amazon-scale active network monitoring. Our team's main project has been a next-generation network monitoring system, to detect and triangulate network problems quickly and accurately in order to drive down MTTD and MTTR. This is composed of a fleet of servers running Jetty and Guice in Java, and a larger fleet of agents written in C++ with Boost.

Software Engineer, NewBay (Dublin, Ireland) (Dec 2008 - Jul 2009):

Working on server farm deployment automation, and large-scale object storage.

Software Engineer, PutPlace (Dublin, Ireland) (Nov 2007 - Dec 2008):

Scaling PutPlace's solutions using Amazon's EC2 and S3 web services; implemented a one-click deployment system to deploy fully production-ready grids of EC2-hosted servers.

VP, Apache SpamAssassin (July 2006 - July 2008), Project Management Committee Member, Apache SpamAssassin Project (July 2004 - present):

Deciding the architecture, development, goals and direction of the open-source Apache SpamAssassin project. see .

Technical Advisory Board Member, MailChannels Corporation (2007 - Jul 2009):

Advising MailChannels on anti-spam issues on an infrequent basis.

Consultant,, Inc. (telecommuting) (Feb 2006 - Nov 2007):

Implemented a machine-learning classifier to differentiate between web pages of different vertical markets at high speed, accurately; developed new scaling code for the Vast backend using Amazon's web services (EC2, S3, SQS and SimpleDB).

SSE, McAfee, Inc. (telecommuting) (Dec 2002 - Feb 2006):

Working for McAfee's enterprise anti-spam department, developing the McAfee SpamAssassin SDK, based on the Deersoft SpamAssassin engine with proprietary enhancements, and on backend systems used to generate and publish high-accuracy anti-spam rulesets. This was the anti-spam software used in McAfee's high-end groupware and appliance product line.

Consultant, Deersoft (telecommuting) (Sep 2002 - Dec 2002):

Commercial version of SpamAssassin, providing proprietary features and speed and efficiency increases. My code quintupled the speed of the core SpamAssassin engine, through use of a more efficient parallel string-matching algorithm. Deersoft was acquired by McAfee in Dec 2002.

Maintainer, SpamAssassin (June 2001 - July 2004):

Creator and maintainer of the open-source SpamAssassin spam filter, . I released the first version of SpamAssassin in 2001. See the "OPEN-SOURCE SOFTWARE" section below for more details.

Head of Software Engineering, Netnote International (Dublin, Ireland) (May 2000 - Sep 2002), Chief Architect, Netnote International (Dublin, Ireland) (Jan 1999 - May 2000):

Design and implementation of the software for the "Webnote", a low-cost internet appliance; embedded system work using C on QNX. UI design was a major factor in this work, as it was aimed at first-time computer users. Later, reoriented the product towards use as a public internet kiosk; design and implementation of telemetry, metering systems, and kiosk network management systems. Ported the software from QNX to Linux. Built up to a 5-person software team.

Senior Software Engineer, Iona Technologies (Dublin, Ireland) (1997 - Jan 1999):

Design and implementation of the "Wonderwall" firewall proxy server for Iona's product range. This product allowed CORBA invocations across the internet and through internet firewalls, while allowing firewall administrators to selectively block or permit access. It was implemented in C++ on Solaris, Linux and Windows, incorporated its own CORBA IIOP implementation, HTTP server, and SSL support. Secure programming techniques were used throughout. I also designed and implemented HTTP tunnelling and SSL support in OrbixWeb, Iona's Java implementation of the CORBA standard.

Software Engineer, Iona Technologies (Dublin, Ireland) (1992 - 1993), Systems Administrator, Iona Technologies (Dublin, Ireland) (1993 - 1997):

Joined Iona Technologies as one of their first employees, implementing a Motif-based GUI for a UNIX printer driver in C on SunOS 4.1.1. I then became Iona's sysadmin while the company grew from 10 people to over 150; by the latter stage I was head of a 3-person team. The position involved looking after the physical network, the UNIX systems and networks, helpdesk, a multi-site email network with SMTP, backups, user account synchronisation and availability across the wide range of internal OSes, and running Iona's main internet servers, net connection and firewall.


In addition to the commercial software development experience detailed above, I am the author of a number of free / open-source software projects. Highlights:

Apache SpamAssassin, a mail filter to detect and block unsolicited bulk email. Since I created the first version in 2001, it has been a runaway success. By now it is deployed by thousands of sites protecting somewhere around 100 million users world-wide, is the #1 open-source spam filter, winner of several awards including the Anti-Spam category in Datamation's Product of the Year 2005 and 2006 Awards, an InfoWorld Bossie Award in 2007, and a Linux New Media Award 2006. It is probably the most widely-used spam filter in the world. More info at .

PLP (the Public Line Printer system). A drop-in replacement for the UNIX "lpr" line printer spooler system, with features oriented towards providing support for networked printers, and improved security. I took over maintainance of this from its original author, and updated and supported it for a year and a half; during my stewardship it eventually had over 10,000 users in over 100 sites, including BASF, the Burlington Coat Factory, and McMurdo Base, Antarctica. PLP was included in SuSE Linux, among other Linux distributions, for several years.


I am a Member of the Apache Software Foundation.



My interests include: SCUBA diving (PADI Advanced Diver certified), reading, graphic design, copyright law, and open source software. I write a weblog at , which won Best Technology Blog in the 2009 Irish Blog Awards.


1989 - 1990: BA degree in Mathematics, Trinity College, Dublin, Ireland; did not complete degree.