Guardian Digital's Open Source Projects

Guardian Digital's Involvement with & Contributions to Open Source

EnGarde Secure Linux

The foundation of Guardian Digital’s EnGarde Cloud Email Security, it is the operating platform that enables our secure end-to-end email infrastructure. Built from the ground up by engineers who have been at the forefront of open-source development from the beginning, the platform was designed to be secure and provide ease-of-management and secure network services.


GNU Public License

The GNU General Public License is a popular license used for many open source programs that allows users to change and share all versions of a program. This is as compared with proprietary licenses which restrict how, where, and for how long a particular application can be used.

The Linux Kernel

The Linux kernel is a key component of the EnGarde Cloud Email Security. It provides true multi-tasking, virtual memory, shared libraries, memory management, and multi-stack networking, including IPv4 and IPv5. Guardian Digital applies its own security enhancements to the stock Linux kernel to increase its already high-levels of security.


Apache Web Server

The most popular web server on the Internet since 1996, the Apache HTTP Server is the industry standard. More than 70% of the domains on the Internet use Apache to serve their websites.

Mariadb Database Server

MariaDB Server is one of the most popular database servers in the world. It’s made by the original developers of MySQL and guaranteed to stay open source. Notable users include Wikipedia, and Google.


Postfix Mail Transfer Agent

Postfix is a Mail Transfer Agent programmed to have a strong emphasis on security as well as extremely fast performance.


BIND is the most popular DNS server in use on the Internet and provides a robust and stable architecture for constructing a domain lookup system. The EnGarde Cloud Email Security includes a specially configured installation of BIND in order to limit security vulnerability exposure.



OpenSSH is an open-source protocol suite that provides encryption for network services like remote login and remote file transfer.


SELinux is an open-source extension to Linux that creates a security protocol that restricts each application on the system to perform only the actions required for normal operations, thereby preventing the exploitation of security flaws. EnGarde uses SELinux and other security controls to strictly limit all running applications to provide the highest possible level of security.



Perl is a popular scripting language ideal for text processing and the automation of system administration tasks. Perl is an integral part of the internals of the EnGarde Cloud Email Security.


PHP is also a popular general purpose programming language. Guardian Digital uses it to rapidly build applications for our client, including WebMail and our graphical user administration system. It is secure and easily integrates with databases.



Through the use of SpamAssassin as a framework for our email security solutions, Guardian Digital is able to help organizations protect their data from all forms of email attacks. SpamAssassin is a flexible, robust scoring framework and plug-in that integrates a wide range of advanced heuristic and statistical analysis tests on email headers and body text. The level of flexibility of SpamAssassin’s flexibility, combined with efficiency upgrades with every release, means that Guardian Digital can continually provide a best-in-class email security solution to some of the largest organizations in the world, and do it much more cost-effectively than conventional solutions.

Apache Hadoop

The Apache Hadoop software library is a framework that allows for the distributed processing of large data sets across clusters of computers using simple programming models. This enables Guardian Digital to be able to manage large volumes of data rapidly and to thereby provide better resource management.



OpenStack is a cloud-operating system that controls large pools of computer, storage, and networking resources throughout a datacenter to help with resource and management of a more optimized infrastructure for the types of workloads our customers require.

Netfilter / IPTables

Netfilter and IPtables are the Linux firewall implementation used to provide stateless and stateful packet filtering, network address translation, and IP masquerading. Guardian Digital uses netfilter as the basis for its easily configurable and powerful firewall implementation.



MRTG is the Multi Router Traffic Grapher, a tool to monitor the traffic load on network links. MRTG generates graphical reports allowing users to view live visual representation of network traffic. Guardian Digital incorporates MRTG to provide this traffic analysis as well as graphs of CPU and RAM usage.


OpenSSL is an open source toolkit implementing the SSL and TLS network encryption protocols. Guardian Digital uses this toolkit to provide secure web services and certificate management as well as general purpose cryptography functions.



PAM stands for Pluggable Authentication Modules, and it’s used by other programs to handle difficult security processes, like authentication. Guardian Digital builds PAM into the system to allow for easier customization of authentication mechanisms.


Rsync is an open source utility that provides extremely fast file transfers for backup and data replication purposes by only transmitting the changes since the previous transfer.



Snort is an open source network intrusion detection system, capable of performing real-time traffic analysis and packet logging on IP networks. An integral security component to many of Guardian Digital's award-winning security solutions, Snort utilizes protocol analysis functions, content searching/matching applications to proactively detect both common and uncommon Internet attacks such as buffer overflows, stealth port scans, CGI attacks, OS fingerprinting attempts, and much more.

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