A Wiki is a collaborative platform for information creation that takes online collaboration to a whole new level. Wikipedia is a classic example of how powerful a Wiki can get.

The form that it takes on Wikipedia is of a very open nature, allowing just about anyone to add, edit and delete content. While conventional thinking does give pause to the approach taken, the underlying thought here is that the constructiveness of users far outweighs their destructiveness, and so far this has proved to be true. However there have been a number of controversies  that have sprung up as a result of this, mostly dealing with two opposing views around a subject which after numerous edits and counter edits end up being locked down by moderators.

While this model does seem to prevail in the world wide web Corporations have a much lower level of tolerance for such “complexities”. To implement a wiki within an organization would require a tremendous focus on security controls. This being said there has been a noticeable difference in their willingness to implement certain “Web 2.0? tools.

There are a number of Wiki tools out there ( Open source and otherwise ). Choosing the right one would depend on the features you are looking for. If security is high on your list of items and your company is already leveraging a CMS like Sharepoint you might be happy to note that in its current release form i.e : MOSS 2007 there exists a Wiki functionality. However this is a Wiki in its most basic form and one that i would not recommend if you are pursuing a more advanced solution. Though it does address your requirements of hacking and virus protection considering it comes under the umbrella of a Content Management Solution.