Data protection and Infrastructure security

This requirement will cover the issues associated with the protection and recovery of data distributed across multiple hosts within GRID environment as well as with the protection of the infrastructure services.
In this requirement we take a more pessimistic view and consider protection against accidental or deliberate corruption (integrity), protection on effect of failure over time (availability), protection from illegal access (access control, see Distributed access control methodologies).
Availability of data over the grid is a key factor to ensure that data wont disappear. The grid can be dynamic and entities composing this grid can disappear or move. So how can we certify that no datas will be lost during the grid live? Do we need data replication and/or other mechanisms?
Considering access control mechanisms are present, illegal access can nevertheless occur through the possible exploitation of security holes. So we need more active security mechanisms. We can consider transposing on the Grid solutions like intrusion detection or firewall. But in a highly distributed and heterogeneous environment like the Grid, it becomes more difficult to configure these tools in a coherent way to ensure correct protection but also correct accessibility. Adaptive Grids introduce other problems like integrating insecure services, fake entity integration, etc.