Protection and Security
Google Drive Link - Protection and Security
·
Protection
o
Mechanism for controlling the access of processes or users
to the resources defined by a computer system.
o
Mechanism should specify - Controls to
be imposed
o Uses:
§ Improves reliability
of the system by detecting errors and
§ Prevents contamination
of a sub-system by another malfunctioning sub-system.
o Unprotected
data cannot defend against of use of unauthorized user whereas
protection-oriented system can identify authorized and unauthorized usage.
o
Note:-A
system can have adequate protection but still be prone to failure and allow
inappropriate access.
§ Ex:
- when genuine user authentication details are stolen.
·
Security:
o
To defend a system from external and
internal attacks.
§ Ex;-
virus, worm & Denial-of-Service
o
Prevention of some of these attacks is performed
as operating system function on some systems, while others leave the prevention
to additional software.
·
USER IDENTIFIERS:
o
Protection and security require the
system to be able to distinguish among all its users.
o
Most operating systems maintain a list
of user names
and associated user
identifiers (user IDs)
§ Ex:-
Windows NT maintains SECURITY ID(SID)
o
IDs are used by processes & threads
and picked when user is authenticated.
o
GROUP IDENTIFIERS:
§ Define
a group name
and the set of
users belonging to that group.
§ Ex:-selected
set of users may only be allowed to read the file.
§ A
user can be in one or more groups
§ The
user's group IDs are also included in every associated process and thread.
o
Escalate privileges:- to gain extra
permissions for an activity
§ Ex:- In Unix,
“setuid” attribute is used to modify the id of the current user as id of owner
of the file ( until extra privileges turned off or program termination).
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