developers and users of the software (an overlapping community in many cases). Obvious failure to perform is easily recognised as a bug, as is failure to conform to appropriate published standards. Security related failings (exploits or vulnerabilities) are clearly bugs too. Each of these kinds of bugs is usually addressed with speedy fixes wherever possible and Open Source advocates will claim very rapid time-to-fix characteristics for software. Severe defects tend to be fixed within hours of their being detected, a process wich is undoubtedly assisted by the availability of the source code. Able developers who discover a bug will commonly also fix it and then report it to the maintainers as well as issuing an updated version of the software on their own authority. Users of the software can choose whether to use the unofficial fix or wait for an `official' version. By `official' we mean a release blessed by the project team itself or a trusted authority such as one of the main distributors of Open Source packages. This mechanism clearly works very well in practice. The pattern with closed-source software is typically that a defect report needs to be filed and then there will be a delay before the vendor determines when or whether to issue an updated release. Users of the software are much more at the mercy of the vendor's internal processes than with the Open Source arrangement and the personal experience of the authors is that it can be extremely frustrating to move from the