Protected System Resources:
The first two layers of the Java security model are primarily concerned along with protecting the security model itself. That's the third layer, the library implementation, in that explicit measures are taken to protect against the categories of attacks listed in Table 2. These resources fall into six categories, as listed in Table 2.
Table Resources checked by Java security
The 3rd layer of the security model isn't just concerned along with protecting system resources; it also gives protection for a few Java runtime resources, to protect the integrity of the security model itself.