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Operating System and Computer Security What does Operating System do
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| Sana | 26.12.2019 | | Hajmi | 32.96 Kb. | | #5153 |
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 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 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 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.
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