home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Dr. CD ROM (Annual Premium Edition)
/
premium.zip
/
premium
/
DOSUTIL1
/
ACSA.ZIP
/
INTRO.DOC
< prev
next >
Wrap
Text File
|
1992-04-08
|
5KB
|
140 lines
A C S A
I N T R O D U C T I O N
The ACSA Software System is designed for IBM/PC compatible hardware both
as a means of access authorization to the hard disk data and a universal means
of "anti-virus" protection.
Shared use of a PC by several users can cause problems of data protection
of one user from intentional or unintentional destruction (updating, copying
etc) by other users. "Virus" infection of computers is a special case of such
interference.
This is quite frequently the trouble with the beginners though sometimes
even experienced programmers have to face such problems, especially if they are
working in the shared mode.
Now, just imagine that you are able:
- to protect your COM, EXE, BAT-files and the BOOT-record from updating;
- to "close" your sub-directories and/or files for other users (but not
necessarily for all of them), so that your files are either absolutely
inaccessible or have a Read-Only access;
- to set the limits of hard disk space for every user;
- to make hard disk inaccessible when booting from a floppy disk drive.
You will have all these advantages with ACSA programming package!
BASIC CONCEPTS AND POSSIBILITIES OF THE SYSTEM
Every user working with a PC is identified within ACSA by means of a unique
code (USER CODE) which he enters at the very start with the LOGIN command.
Each file on the hard disk belongs to some user and that user is the FILE
OWNER. The FILE OWNER sets an ACCESS MODE for each file:
W - the access to a file is WRITE/READ/EXECUTE;
or
R - the access to a file is READ/EXECUTE;
or
X - the access to a file is EXECUTE
or
"-" - no access.
The FILE OWNER may set an ACCESS MODE to any of his files for other users.
For example:
W - FOR ME, R - FOR OTHER USERS
or
W - FOR ME, no access FOR OTHER USERS.
So, each file has its OWNER and its ACCESS MODE ( either W, R, X or "-" both
for the OWNER and for OTHER USERS).
OTHER USERS are subdivided into users which belong to the same group as the
OWNER or into "outsiders".
The notion USER GROUP means any association of users (a group of students, or
a group of programmers working at the same task, etc).
Thus, the FILE OWNER may set:
- file access (W, R, X, or "-") for himself (the USER);
- file access (W, R, X, or "-") for users from the same GROUP;
- file access (W, R, X, or "-") for outsiders (all OTHERS).
A file may also have no OWNER. In this case all users will have access to
this file without any restrictions.
So, every user has his USER CODE (login name), and every file has its FILE
OWNER, GROUP CODE, and ACCESS MODES for User, Group and for Others ("UGO").
Pressing F2 in ACSA Commander lets you change the "mode" of a file or files.
Under ACSA Commander's "MOD" (mode) column, the three letters represent User,
Group and Others; and each letter can be either "w" or "r" or "x" or "-".
How to manage user access to a file:
- If the USER CODE and the FILE OWNER CODE are the same, ACSA verifies the
OWNER ACCESS MODE. If the "intentions" of the user fit the code the
operation is executed (for example: the user wants to read a file and the
ACCESS MODE is R or W).
- If, on the contrary, the user wants to write in a file and the ACCESS MODE
is R or X, then the operation is not executed.
- If the USER CODE and the FILE OWNER CODE are not the same, i.e. the file
belongs to another user, then it is necessary to verify the following:
1. Whether the user who "encroaches" upon other users' property belongs
to the same GROUP as the FILE OWNER.
2. If they are in the same group, the ACCESS MODE to the file set by the
FILE OWNER for the members of the GROUP is verified.
3. If they do not belong to the same group, the ACCESS MODE for OTHERS
is verified.
The ACCESS MODE verification for other users is the same as for the FILE
OWNER with respect to his file.
How to set USER CODE, FILE OWNER CODE, ACCESS MODE and USER GROUP CODE:
The USER CODE is entered from the very start by the LOGIN command from the
AUTOEXEC.BAT file right after the operating system boots up. USER CODE may be
changed by the LOGIN and USER commands.
All computer users must be registered, i.e. their CODES must be entered in
a special ACSA.DIR file. Only a SYSTEM ADMINISTRATOR (SUPER USER) has access
to this file. SYSTEM ADMINISTRATOR has at least read-access to all the files
of all the users, and can change access levels on any file or directory. He is
not the person to argue with!
The FILE OWNER CODE, USER GROUP CODE, ACCESS MODES may be set with the help
of ACSA commands or the special file manager named ACSA Commander.
When a new file is created, ACSA automatically registers the information
concerning the FILE OWNER, USER GROUP CODE and ACCESS MODES:
FILE OWNER = USER CODE (login name)
USER GROUP CODE = GROUP CODE of the current user;
ACCESS MODES = W for oneself, "no access" - for the others.
This default mode may be changed by entering the AMOD command.