Active Networks is a network infrastructure which is programmable on a per-user or even per-packet basis. Increasing the flexibility of such network infrastructures invites new security risks. Coping with these security risks represents the most fundamental contribution of Active Network research. The security concerns can be divided into those which affect the network as a whole and those which affect individual elements. It is clear that the element problems must be solved first, as the integrity of networklevel solutions will be based on trust of the network elements. In this

This report presents a characterization of text documents from the Portuguese Web. This characterization was produced from a crawl of over 4 million URLs and 131 thousand sites in 2003. We describe rules that we established for defining its boundaries and the methodology used to gather statistics. We also show how crawling constraints and abnormal situations on the Web can influence the results.

To reduce the likelihood of conflict and confusion, a few top level domain names are reserved for use in private testing, as examples in documentation, and the like. In addition, a few second level domain names reserved for use as examples are documented.