Operating System and Computer Security What does Operating System do

Operating System and Computer Security

What does Operating System do

• Manages all the resource in a computer (including processor, memory, i/o devices)

• Provides an interface between the hardware and application software.

Mostly used OS

• Desktop

• Windows

• Mac OS

• Unix/Linux and their siblings.

• PDA

• Palm

• Pocket PC

• Embedded Linux OS

Macintosh Operating System

• Evolved from 1984’s original MacOS

• 1984 Mac was first commercial computer with Graphical User Interface (GUI) and mouse

• Currently MacOS 9, MacOS X

• Inventor of trash can, alias (shortcut), pull-down menus, etc.

Mac OS Details

• Control Strip

• Alias (same as shortcut)

• Single-button Mouse (can be customized)

• Sherlock 2 (global search utility, copied in Windows 2000 and Windows ME)

• Easy to use, hard to troubleshoot

Windows OS

• Windows is built on top of MS-DOS, the MicroSoft-Disk-Operating-System, based QDOS.

• Windows 1.0 very delayed, very poor quality

• Windows 3.1 (c. 1992) first usable version, still very limited in comparison to MacOS 6

• Windows 95 revolutionary for Intel based computers, but, just a copy of Mac OS

Windows 95

• Stole Recycle Bin, Shortcuts, and Menu System from Macintosh OS

• Excellent user-friendliness for operations

• Like MacOS, suffers from un-friendliness for troubleshooting

• Excellent multi-tasking capabilities (run multiple programs)-uses virtual memory

Multi-tasking

• The ability to run several programs at the same time.

• CPU can only run one program at a time. OS will switch programs for it. Since the switching is so fast, it looks like running multiple programs at the same time.

• Two multi-task mechanism

• Cooperative multi-tasking (program voluntarily release CPU )

• Preemptive multi-tasking.(OS deprives the CPU control when time is up)

Windows History

• Windows 95 for home machines, stable, simple

• Windows NT 4.0 for business/office computers

• Windows 98 replaces 95, very unstable, just a facelift

• W98 Release 2 much better, still sucked

• Windows 2000 replaces Win NT 4.0

• Incredibly stable, not very backwards compatible

• Windows ME (Millennium Edition) replaced W98 (fall 2000)

• Almost no new features

• Seems a little more stable than W98

• Faster Startup

Windows XP

• Released last year

• Home version and business version based on same OS

• Previously, Win NT & 95 different, 2000 and ME different

• More stable than Win 98/ME, not as stable as W2000

Linux and Unix

• Unix was the first usable OS and still widely used today. It runs on special computers, e.g. Sun, Silicon Graphics, HP, DEC

• Linux was a miracle, initalized by Linus Torvalds and maintained by programmers all over the world.

• Both are based on a stable command line OS

• By comparison, Windows based on unstable command line OS, MS-DOS

• Both Linux and Unix use an X-Windows GUI

Ranking the Operating Systems

• Unix

• Linux

• Mac OS X

• Windows 2000

• Mac OS 9

• Windows NT

• DOS

• Windows 95

• Windows ME

• Windows 98

• Mac OS 9

• Windows ME/98/95

• Mac OS X

• Windows 2000/NT

• Linux

• Unix

• DOS!

Future of Operating Systems

• Microsoft must address stability problems in home computers – Windows XP was a small step

• Linux becomes more popular, but only for advanced users and in server market.

• Macintosh’s market penetration more based on hardware appeal rather than software

• In old days, Macs succeeded because they were the only GUI on the block. People bought Macs for the software

• Windows is such a good copy that hardware, reliability, and price is now a big reason for the purchase of a Macintosh

Computer security challenges

• Virus

• Email Virus

• Worm

• Trojan Horse

• Spam

Virus

• Viruses are fragments of computer code that can piggyback on the normal programs

• When normal program is infected by virus, virus will run first every time you start the program.

• Viruses can duplicate themselves and infect other programs.

• Original virus are less and less popular now.

• People don’t copy files from others, but would rather download from the original source.

• Anti-virus software is widely used.

Email virus

• An e-mail virus moves around in e-mail messages, and usually replicates itself by automatically mailing itself to dozens of people in the victim's e-mail address book.

• Two kinds

• Executable attachment (.exe .vbs .com .bat files).

• Macro language viruses.

Fact about email virus

• BOTTOM LINE :There is *NO* such thing as an E-mail text virus!

• You can not get a virus or any system damaging software by reading an e-mail*. E-mails (that is, the ACTUAL message can not contain viruses)

• Email viruses always resides in the attachment. So don’t run any suspect attachment files.

Worm

• A worm is a computer program that has the ability to copy itself from machine to machine by taking advantage of the security hole in the system.

• Security holes are bugs in the OS.

• This is the most serious threat now

• Your Computer can be infected by just plugging in the internet.

• MSblast and SoBig are the recent worms that damage hundreds of thousand computers.

Trojan Horse (back door)

• A Trojan horse is simply a computer program. The program claims to do one thing (it may claim to be a game) but instead does damage when you run it (it may erase your hard disk).

• Trojan horse usually does replicate itself.

Suggestions to secure your computer

• Use anti-virus software.

• Update your computer regularly.

• Be careful with the email attachments

• Safe: .jpg .bmp .pdf .txt ….

• Unsafe: .exe .doc .xls .ppt …

• Avoid email software by Microsoft (outlook, outlook express…). They are mostly targeted.

• Use firewall or router to protect you from worm attack.

Spam (junk mail)

• Spamming is business

• Most effective way to stop it is legislation. Most states passed law to restrict it, but none fully banned it.

• How spammers get your mail.

• Web search

• Sending test emails

• Exchange or buy from other spammers

• A case study: How an can HTML email reveal your identity.

Suggestions to fight spam

• Never reply junk emails

• Moreover, never even open them.

• Don’t post your actual email address in the website.

• Sparty_at_msu.edu

• Sparty@NOSPAMMINGmsu.edu

• Use a picture of your email address.

• When send group emails, put all the recipients in the BCC field to protect other people.