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Showing posts with label os. Show all posts
Showing posts with label os. Show all posts

unix os hardening notes

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Operating System Hardening is an essential security strategy positioned between the network and application. One of popular server OS - Unix is a multi-user system, which could support over hundreds of users with different directories and database applications. Unix is less secure than other proprietary operating systems as its public-domain variants are particularly vulnerable. That's is why hardening Unix is becoming essential parts of each organization. HiTRUST provides UNIX Hardening service to minimize servers' exposure to current and future threats on this computer platform by fully configuring the operating system, removing unnecessary applications and apply security-related patches offered by your vendor.

Hardening Unix server raises the bar on the level of skill and effort needed to crack into system, thus discourages joyride attackers looking for an easy target. HiTRUST also helps to log all network-access hacking attempts to the Unix server, both successful and unsuccessful. By logging suspicious network activity, an organization can stop would-be attackers from breaking into the system; more importantly, the organization can trace (and sometimes identify) successful attackers.

Common hardening task aims to protect system against:


Denial-of-service attacks


Brute-force attacks

Social-engineering attacks

Passive attacks

Malicious local users

Legitimate users' clumsiness

Software bugs, etc.


How to make your machine more secure
(And easier to keep up to date on patches because there'll be fewer patches you need to apply)

  1. Most of what we'll be doing involves turning off unneeded services in /etc/inetd.conf.
    • Go ahead and edit /etc/inetd.conf. Entries that have a "#" are a comment. All those lines that aren't commented out, are services that are launched by inetd. The odds that any given one of these services will develop a (known) security hole isn't that high, but the odds that any one of them will is noticeably higher. So we want to turn off all the unneeded ones.
    • Services we recommend always turning off include: echo, daytime, chargen, time.
    • Services we recommend turning off if you can include... everything else. If this isn't a mission critical machine, we'd actually recommend that you turn off everything, and then add back services you later discover you needed. Of course, on a machine that must be available, it's better to only turn off services you know you won't need.
    • For specifics of how to turn off a service that's launched by inetd, see Turning off an inetd-launched service.
  2. Not all network services on UNIX are launched by inetd. Some run as standalone daemons. Sendmail and Samba are both packages that have the option of either running off of inetd, OR running as standalone daemons.
    • If you don't need to process e-mail on this machine (including local e-mail), we recommend turning off sendmail. See turning off sendmail for specifics.
    • If you don't need to share files or printers from your UNIX machine to machines running Microsoft operating systems, we recommend turning off samba. See turning off sambafor specifics.
    • Note that you may have other network services that are not launched by inetd. These are only two of the most common.
    You're done. For now.

os, operating system 20 marks and 80 mark MSBTE third year fifth semester co,cm,cd,if CO/cd/cm/if SAMPLE question paper

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Sample Test Paper - I

Subject

: Operating System

Max Marks : 20

.

Q.1 Attempt any Two of the following.------08 Marks

a) State and explain different Operating System services.

b) Explain process control block with suitable diagram.

c) What is mean by Operating System? Write difference between multitasking and

multiprogramming.



Q.2 Attempt any Two of the following.----------12 Marks

a) Write different types of Operating System structure. Explain any two in detail.

b) Explain following terms

i)Multiprocessor systems.

ii)Distributed systems.

iii)Clustered Systems.

c)

i) Explain file management.

ii) What is mean by system call? Write system calls for process control.




Sample Test Paper - II

Subject

: Operating System

Max Marks : 20

Q.1 Attempt any Two of the following.08 Marks

a) Define thread. State the benefits of threads.

b) Explain Round Robin (RR) scheduling algorithm with suitable example.

c) What is Deadlock? How to prevent Deadlock?


Q.2 Attempt any Three of the following.12 Marks

a) Explain the following terms.

i)Sequential access method.

ii)Direct access method.

b) What is Virtual Memory? Explain the concept of Paging.

c) Explain the following terms.

i)First In First Out (FIFO).

ii)Least Recently Used (LRU).

d) Explain any two allocation methods.



Sample Question Paper - I

Course Name : Computer Engineering Group

Course Code : CO/CM/CD/IF

Semester: Fifth

Subject: Operating System

Max Marks : 80

Time: 3 Hours



Q.1 Attempt any FOUR of the following.16 Marks

a) What is Operating System? Explain the concept of time sharing.

b) State uses of system calls.

c) State and explain different process states.

d) State the concept of mutual exclusion.

e) Explain with suitable diagram layered and monolithic operating system structures.

f) Explain concept of swapping with diagram.


Q.2 Attempt any THREE of the following.-------12 Marks

a) State and explain different operating system services.

b) Differentiate between sequential and batch processing.

c) What do mean by scheduler? State types of scheduler.

d) Differentiate between Pre-emptive and Non-emptive scheduling.


Q.3 Attempt any TWO of the following. -------12 Marks

a) What is booting? Explain the concept of device management.

b) Write different types of operating system structures. Explain any two with suitable

diagram.

c) What is process? Draw process state diagram and state its meaning.


Q.4 Attempt any TWO of the following.16 Marks

a) Explain in detail multithreading models with suitable example.

b) What is Deadlock? Explain concept of critical region and Deadlock handling.

c) Differentiate between the following terms

i)Contiguous and Linked allocation.

ii)Linked and Indexed allocation.


Q.5 Attempt any THREE of the following.-------12 Marks

a) Differentiate between multitasking and multiprogramming.

b) State real time and multiprocessor system.

c) State and explain operations on processes.

d) Explain CPU and I/O Burst cycle with suitable diagram.


Q.6 Attempt any TWO of the following.----12 Marks

a) Solve the following problem by using following scheduling algorithms

Processes Burst Time

  • 1
  • 27
  • 2
  • 6
  • 3
  • 3

i)FCFS.

ii)SJF.

iii)Round Robin.

b) Explain different free space management techniques.

c) Explain the FIFO, Optimal and LRU page replacement algorithm for the reference string,

7 0 1 2 0 3 0 4 2 3 1 0 3.



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