The Apache HTTP Server Project is an effort to develop and maintain an open-source HTTP server for modern operating systems including UNIX and Windows NT. The goal of this project is to provide a secure, efficient and extensible server that provides HTTP services in sync with the current HTTP standards

mod_php embeds a persistent PHP interpreter in the Apache webserver. Thus overhead of starting an external interpreter and avoids the penalty Interpreter start-up time, thus accelerating PHP based dynamic content

as mod_php only it embeds the Perl Interpreter.

as mod_php only it embeds the Python Interpreter

provides strong cryptography for the Apache webserver via the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1) protocols by the help of the Open Source SSL/TLS toolkit OpenSSL. In a word its what make the https protocol possible in  the Apache webserver.

Libmcrypt, which contains encryption functions, and provides a standardized mechanism for accessing them. Use by PHP

Mhash is a free (under GNU Lesser GPL) library which provides a uniform interface to a large number of hash algorithms. These algorithms can be used to compute checksums, message digests, and other signatures. Used by PHP

OSSP mm is a 2-layer abstraction library which simplifies the usage of shared memory between forked (and this way strongly related) processes under Unix platforms. Used by PHP

Modular Calendar Access Library. libmcal is a C library for accessing calendars. It's written to be very modular, with pluggable drivers. One of the main drivers it handles is ICAP. ICAP is an internet protocol that has very close ties with the IMAP protocol. Using ICAP, you can access a calendar in very much the same way as you use IMAP to access a remote mailbox

wv is a library and access which allows access to Microsoft Word files. It can load and parse Word 2000, 97, 95 and 6 file formats. (These are the file formats known internally as Word 9, 8, 7 and 6.) There is some support for reading earlier formats as well: Word 2 docs are converted to plaintex.

is a library for reading vector images in Microsøft's native Windøws Metafile Format (WMF) and for either (a) displaying them in, e.g., an X window; or (b) converting them to more standard/open file formats such as, e.g., the W3C's XML-based Scaleable Vector Graphic (SVG) format.

GD is an open source code library for the dynamic creation of images by programmers. GD is written in C, and "wrappers" are available for Perl, PHP and other languages. GD creates PNG, JPEG and GIF images, among other formats. GD is commonly used to generate charts, graphics, thumbnails, and most anything else, on the fly.

ImageMagick®, is a free software suite to create, edit, and compose bitmap images. It can read, convert and write images in a large variety of formats. Images can be cropped, colors can be changed, various effects can be applied, images can be rotated and combined, and text, lines, polygons, ellipses and Bézier curves can be added to images and stretched and rotated.

Netpbm is a package of graphics programs and a programming library. There are over 220 separate programs in the package, most of which have "pbm", "pgm", "ppm", "pam", or "pnm" in their names.

PostNuke is one of the most powerful open source content management systems in the world (source http://www.postnuke.com).  (XSecHosting: With over 1000 themes and masses of modules there probably right, hence this is the XSecHosting recommended CMS).

XOOPS is an extensible, OO (Object Oriented), easy to use dynamic web content (XSecHosting: Not quite as many modules, themes as Postnuke. There is a debate as to whether or not it is as easy to use as PostNuke!). 

TYPO3 is a free Open Source content management system for enterprise purposes on the web and in intranets. It offers full flexibility and extendability while featuring an accomplished set of ready-made interfaces, functions and modules. (XSecHosting: Truely a stellar Effort by a 'brother', however there is currently a lack in the themes department).

AWStats is a free powerful and featureful tool that generates advanced web, streaming, ftp or mail server statistics, graphically. This log analyzer works as a CGI or from command line and shows you all possible information your log contains, in few graphical web pages.

The Webalizer is a fast, free web server log file analysis program. It produces highly detailed, easily configurable usage reports in HTML format, for viewing with a standard web browser.

The OpenSSL Project is a collaborative effort to develop a robust, commercial-grade, full-featured, and Open Source toolkit implementing the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1) protocols as well as a full-strength general purpose cryptography library

OpenSSH is a FREE version of the SSH protocol suite of network connectivity tools. OpenSSH encrypts all traffic (including passwords) to effectively eliminate eavesdropping, connection hijacking, and other network-level attacks.  XSecHosting users use scp/sftp to upload webpages, with various appropriate client software (see below: )

GnuTLS is a project that aims to develop a library which provides a secure layer, over a reliable transport layer. Currently the GnuTLS library implements the proposed standards by the IETF's TLS working group. Some Subsystems seem to prefer this implementation instead of  openSSL.

provides process interface to the kernel encryption functions in the form of loopback devices, used for creating encrypted swap space (XSecHosting recommends encrypting swap space) and other disk partitions/filesytems.

an implementation of IPSEC & IKE for Linux. IPSEC is Internet Protocol SECurity. It uses strong cryptography to provide both authentication and encryption services. Authentication ensures that packets are from the right sender and have not been altered in transit. Encryption prevents unauthorised reading of packet contents.

provides the eMail/File level digital signing and (en/de)crypting functions, used in Squirrelmail (the XSecHosting webMail tool) and enigmail the transparent Mozilla (the BCIGNet recommended browser/email suite) emailer plugin (works with Thunderbird too).

Provides the peered XSecHosting public key service used by GnuPG in the Squirrelmail (the XSecHosting webMail tool) and enigmail the transparent Mozilla (the BCIGNet recommended browser/email suite) emailer plugin (works with Thunderbird too).

The OpenCA Project is a collaborative effort to develop a robust, full-featured and Open Source out-of-the-box Certification Authority implementing the most used protocols with full-strength cryptography world-wide. XSecHosting CA Services uses OpenCA to maintain it's server certificate  infrastructure.

Snort is an open source network intrusion prevention system, capable of performing real-time traffic analysis and packet logging on IP networks. It can perform protocol analysis, content searching/matching and can be used to detect a variety of attacks and probes, such as buffer overflows, stealth port scans, CGI attacks, SMB probes, OS fingerprinting attempts, and much more. Over the years Snort has evolved into a mature, feature rich technology that has become the de facto standard in intrusion detection and prevention.

The Snare Micro Server is a program that provides a central collection facility for a variety of log sources.

Snare for Linux provides a 'C2' or 'CAPP' style audit subsystem for the Linux operating sysystem. It can be used as a standalone auditing tool for Linux, or can send data to the Snare Server for analysis and storage.

RazorBack is a GUI log analysis program that interfaces with the SNORT open source Intrusion Detection System to provide real time visual notification when an intrusion signature has been detected on the network.

The Linux Intrusion Detection System (LIDS) is a kernel patch and admin tools which enhances the kernel's security by implementing Mandatory Access Control (MAC).

Firestorm is an extremely high performance network intrusion detection system (NIDS).

AIDE (Advanced Intrusion Detection Environment) is a free replacement for Tripwire. It does the same things as the semi-free Tripwire and more.

ntop is a network traffic probe that shows the network usage, similar to the popular top Unix command

nefu monitors network services and reports outages. Working from a discription of the network topography

checks/informs a server is up and running. as server monitor heart beat forms the basis for High Availability failover solutions

Service Monitoring Process mon is a general-purpose scheduler and alert management tool used for monitoring service availability and triggering alerts upon failure detection.

keepalived is a userspace process for LVS cluster nodes health checks and LVS directors failover

The Linux Virtual Server is a highly scalable and highly available server built on a cluster of real servers, with the load balancer running on the Linux operating system

The Redhat project based on LVS to create load balanced and highly available network services from which ideas and componets where taken.

another project based on LVS to create load balanced and highly available network services from which ideas and components where taken.

Coda is an advanced networked filesystem implementing

Built in to the Kernel with tools part of the Slackware Distibution, mentioned here because of the import role played in High Availabiliy Systems

LVM is a Logical Volume Manager for the Linux operating system, as RAID it's built in to the Linux kernel with tools part of the Slackware Distribution

OpenLDAP Software is an open source implementation of the Lightweight Directory Access Protocol.

The MySQL database server is the world's most popular open source database. (source http://www.mysql.com)

PostgreSQL is a highly scalable, SQL compliant, open source object-relational database management system

Usermin is a web-based administration interface for users. XSecHosting users use this module to set things like SpamAssassin detection thresholds, White and Blacklists, and other mail related setting eg for procmail the mail delivery program.