A distributed file system exhibits location transparency if
- The name of a file indicates exactly where the file can be found.
- The name of a file does not indicate where the file can be found.
- The name of a file does not need to be changed when the location of
the file changes.
- The name of a file is not adequate for finding the file.
A file server provides stateless service if
- The files that it provides are not stored physically on that server.
- The files that it provides are stored physically on that server.
- The server keeps track of information about open files on client
machines
- The server does not keep track of information about open files on
client machines.
Local caching of files is common in distributed file systems,
but it has the disadvantage that
- Temporary inconsistencies among views of a file by different
machines can result.
- The file system is likely to be corrupted when a computer crashes.
- A much higher amount of network traffic results.
- Caching makes file migration impossible.
Suppose that somebody replaces the system encryption executable
program by one that encrypts, but that also mails a copy of the
cleartext of the document to
himself. The modified program is called a
- virus
- worm
- Trojan horse
- trap door
If a malicious process is granted temporary administrator-level
access to a system,
- the threat is over as soon as the process is killed.
- the threat is over after the operating system is rebooted.
- the thread is over after rebooting the machine and
replacing files that show a virus infection.
- the threat is often permanent until the entire disk is wiped clean.
The access matrix approach to protection has the difficulty that
- the matrix, if stored directly, is large and can be clumsy to manage.
- it is not capable of expressing complex protection requirements.
- deciding whether a process has access to a resource is undecidable.
- there is no way to express who has rights to change the access
matrix itself.