1. SYSTEM SECURITY & ANTIVIRUS Chapter - 4 1Dr. BALAMURUGAN MUTHURAMAN

2. The meaning of the term computer security has evolved in recent years. Before the problem of data security became widely publicized in the media, most people’s idea of computer security focused on the physical machine. Traditionally, computer facilities have been physically protected for three reasons.  To prevent theft of or damage to the hardware  To prevent theft of or damage to the information  To prevent disruption of service M EANING OF C OMPUTER SECURITY 2Dr. BALAMURUGAN MUTHURAMAN

3. VIRUS A virus is software that spreads from program to program, or from disk to disk, and uses each infected program or disk to make copies of itself. Basically computer damage. 3Dr. BALAMURUGAN MUTHURAMAN

4. The term comes from biology. A computer virus reproduces by making, possibly modified, copies of itself in the computer’s memory, storage, or over a network. Similar to the way a biological virus would work. The very first virus to be created outside the single computer or lab was the program called "Elk Cloner.” It was written by Rich Skrenta in 1982. The virus attached itself to the Apple DOS 3.3 operating system and spread through floppy disk. The virus was originally a joke, created by a high school student and put onto a game. The 50 th time someone played the game, the virus would be released. So instead of playing the game, the user saw a blank screen that read a poem about the virus named Elk Cloner. 4Dr. BALAMURUGAN MUTHURAMAN

5. A VIRUS SPREAD First a programmer writes the virus most often being attached to a normal program; unknown to the user, the virus spreads to other software. Then the virus is passed by disk or network to other users who use other computers. The virus then remains hidden as it is passed on. 5Dr. BALAMURUGAN MUTHURAMAN

6. TYPES OF VIRUSES The way viruses are usually categorized is by what they do.  The boot virus which infects the boot sector of disk storage  The program virus which infects the executable programs  The multipartite virus which is a combination of the boot and program virus  The stealth virus which is able avoid detection by a variety of means such as removing itself from the system registry, or hidden as a system file  The parasitic virus which inserts itself into another file or program such that the original file is still workable  The polymorphic virus which changes its code structure to avoid detection and removal  The macro virus which exploits the macro language of a program like Microsoft Word or Excel. 6Dr. BALAMURUGAN MUTHURAMAN

7. TO PROTECT THE SYSTEM Run a more secure operating system like UNIX, another computer operating system in which you never hear about viruses on these operating systems because the of the security features If you are using an unsecured operating system, you can buy virus protection software like McAfee or Norton AntiVirus To help avoid viruses, it is very important that your computer is current with the latest update and antivirus tools, try to stay informed with recent threats about viruses and that you be careful when surfing the Internet, downloading files and opening attachments 7Dr. BALAMURUGAN MUTHURAMAN

8. WORMS Worms have been around since 1988. A computer worm is very similar to that of a normal computer virus. Unlike a virus though, the worm is a program that can copy itself across a network and it can run on itself. A worm also has a unique feature in the sense it does not have to host program in order to run. A worm works by copying itself into nodes or network terminals which does not require any intervention from the user itself. Worms began to take off in the late ‘90s and early 2000’s. These modern worms ran themselves through the internet and many file sharing programs such as KaZaa, a music file-sharing program. 8Dr. BALAMURUGAN MUTHURAMAN

9. TYPES OF WORMS The “Email Worm” – The email worm spreads itself through email – The worm can hide itself in messages as a link or an attachment that will redirect the user to an infected website. – Many users become losses to this particular worm due to their weakness and willingness to read and open messages that they think could be interesting. The Instant Messaging Worm – This worm masks itself in the form of an “IM” with the contents of a link that will redirect the user to an infected website and then try to gain full access of the machine. 9Dr. BALAMURUGAN MUTHURAMAN

10. PROTECT YOURSELVES Even though it seems impossible to not catch a worm, it is not. One of the best things a computer owner can do is install and run anti-virus software, especially the kind that updates automatically. Anti-virus software will notify the user when a virus or worm is found and prevent it from running and/or copying itself. Other precautions to protect in worm  Choosing secure passwords and changing them regularly  Not opening unfamiliar emails or attachments and most importantly not running or copying software from an unsecured website. 10Dr. BALAMURUGAN MUTHURAMAN

11. VIRUSES VS WORMS 1.Spreads from program to program, or from disk to disk 2.Uses each infected program or disk to make copies of itself 3.Computer damage 4.Destroys data or erases disks 5.Operating system specific 1. Uses computer hosts to reproduce themselves 2. Travel independently over computer networks 3. Software sabotage 4. Resides in memory rather on disk 5. Puts computers at a standstill 11Dr. BALAMURUGAN MUTHURAMAN

12. ANTIVIRUS SOFTWARE Computer programs intended to identify and eliminate computer viruses. 12Dr. BALAMURUGAN MUTHURAMAN

13. ANTIVIRUS SOFTWARE: HOW IT WORKS “Antivirus software is the equivalent to penicillin of the computer world.” Like penicillin, antivirus applications act as a protector over your system, scanning incoming files and applications, “quarantining” or cleaning up unwanted viruses looking to cause harm to your system. Antivirus software is considered to be an aid that detects, fixes and even prevents viruses and worms from spreading to your computer as well as connecting computers. 13Dr. BALAMURUGAN MUTHURAMAN

14. DRAWBACKS OF ANTIVIRUS SOFTWARE  Some antivirus software can considerably reduce performance.  There should not be more than one antivirus software installed on a single computer at any given time.  It is sometimes necessary to temporarily disable virus protection when installing major updates.  Some argue that antivirus software often delivers more pain than value to end users. 14Dr. BALAMURUGAN MUTHURAMAN

15. TWO MAIN TYPES OF ANTIVIRUS There are different types of antivirus software for different computers. Some are designed for personal computers. Some are for servers and others for enterprises. There are mainly two types of antivirus software are Specific Scanning and Generic Scanning 15Dr. BALAMURUGAN MUTHURAMAN

16. SPECIFIC SCANNING Specific scanning also called signature detection The application scans files to look for known viruses matching definitions in a “virus dictionary” then it takes necessary action The specific scanning is not always reliable because virus authors are creating new ways of masking their viruses so the antivirus software does not match the virus signature to the virus dictionary. 16Dr. BALAMURUGAN MUTHURAMAN

17. GENERIC SCANNING Generic scanning is also referred to as the suspicious behavior approach. Generic Scanning is used when new viruses appear. In this method the software does not look for a specific signature but instead monitors the behavior of all applications. If anything questionable is found by the software the application is quarantined and a warning is broadcasted to the user about what the program may be trying to do. 17Dr. BALAMURUGAN MUTHURAMAN

18. Computer viruses and worms can so easily be placed into your work station and you must be careful when going on the internet, opening emails from unknown users, make sure you have some kind of anti-virus software and always get updates then only you are not helping to spread viruses and worms to other people as well as harming yourself and your pocket. 18Dr. BALAMURUGAN MUTHURAMAN