1. Security in nachos Firewall and Virus aditional the code in nachos of security

2. Firewall A firewall is a set of related programs, located at a network gateway server, that protects the resources of a private network from users from other networks.

3. Firewall, working closely with a router program, examines each network packet to determine whether to forward it toward its destination. A firewall also includes or works with a proxy server that makes network requests on behalf of workstation users. A firewall is often installed in a specially designated computer separate from the rest of the network so that no incoming request can get directly at private network resources.

8. public NachosSecurityManager(File testDirectory) {

9. this.testDirectory = testDirectory;

10. fullySecure = Config.getBoolean("NachosSecurityManager.fullySecure");

11. }

13. Lib.assertTrue(this != System.getSecurityManager());

14. return new PrivilegeProvider();

15. }

16. Here it is demonstrated since the way of privilege is in use for accessing by means of the magnement to this function and for realizing the authorization for modifcaciones of files.

18. private class PrivilegeProvider extends Privilege {

19. public void doPrivileged(Runnable action) { NachosSecurityManager.this.doPrivileged(action);

20. }

22. return NachosSecurityManager.this.doPrivileged(action);

23. }

24. public Object doPrivileged(PrivilegedExceptionAction action)

25. throws PrivilegedActionException {

26. return NachosSecurityManager.this.doPrivileged(action);

27. }