Nachos implements security features like a firewall and privilege system to protect system files and resources. The firewall examines packets to determine if they should be forwarded or blocked. Privilege objects can perform privileged actions, like modifying system files, by calling doPrivileged methods on the NachosSecurityManager. This allows authorization for changes to be managed in a centralized way.

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.

4. Security in Nachos In nachos in the safety folder there exist 2 programs which realize the function of the safety of the whole operating system and likewise relizan the authorizations for modficar the files or files of the whole operating system and here estan the codes of nachos.

5. These functions give the orders to create an object that calls favoured which tendra access of several ways to the files that exist in the operating system. public abstract class Privilege () public Privilege() public abstract Object doPrivileged(PrivilegedAction action);

6. Here it appears as the class favoured does not have any restriction to effect changes in the files or properties of these. public abstract Object doPrivileged(PrivilegedExceptionAction action) throws PrivilegedActionException;

7. Here it appears since in the safety program of the administrator removes I end the functions to do the examination and the location to the files of the system.

8. public NachosSecurityManager(File testDirectory) {

9. this.testDirectory = testDirectory;

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

11. }

12. public Privilege getPrivilege() {

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.

17. And finally here it appears where it is possible to realize the final authorization and likewise begin with an extencion thus and this way to be able to modify the files of the system.

18. private class PrivilegeProvider extends Privilege {

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

20. }

21. public Object doPrivileged(PrivilegedAction action) {

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

23. }

24. public Object doPrivileged(PrivilegedExceptionAction action)

25. throws PrivilegedActionException {

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

27. }