How Viruses are spread on our computer

Today I am back with my new topic which is based on How Viruses are spread on our computer

Let's start !!

A program that has the capability to infect other program and make copies of itself and spread into other programs is called Virus. A Virus can be identified if our system:

•    Takes a long time to load applications.
•     Has an inability to boot.
•     Shows unpredictable program behavior.
•     Has strange graphics appearing on the screen.

The types of viruses are: 

File Virus, which infects and replicates when it gets attached to MS-DOS program files with EXE or COM extensions.

Boot Sector virus infects the boot sector of the floppy disk or hard disk.

 

Macro Viruses insert unwanted words or phrases in MS Word or Excel.

How Viruses are spread?

It seems to be a common belief that viruses are spread by games, by Internet file downloads or by Bulletin Board Systems (BBSs). The truth is more intricate. A physical disk has to be involved in case of a boot sector virus, whether it contains any software or not. You cannot get a boot sector virus by using a BBS.

The most likely routes by which a virus gets into an organization are engineers, parents, or colleague:

•   Hardware engineers use disks on a large number of computers. This increases their chances of picking up an infected disk and spreading a virus.
•   Parents have children, and if there is a PC at home, and the children are young teenagers, then they quite possibly swap software at school. The disks that they bring home might well be infected, and if the parent is taking disks to and from work, a virus could easily be taken into work.
•   A  boot sector virus could be on a data disk obtained from a friend or relative. 
• The commonest way for a macro virus to enter a company is as an attachment to an Email.

Other ways of getting a virus include:

1. Shrink-wrapped software.→  Some of the largest companies have accidentally shipped a virus in shrink-wrapped software.
2. Purchased Hardware.→  Most hardware comes with disks containing utilities or drivers.
3. Sales Persons Running Demonstration.→  They could unwittingly install the virus they picked up from the last place they ran their demonstration.
4. Pirated Software:→  Commercial software is usually scanned for any viruses. On an average, pirated software can definitely have a virus. 

Damage Done By Viruses

The major damages done by viruses are discussed below:→

1.  Trivial Damage.→ This is the most insignificant damage done by the virus (e.g., Form). It will simply make the speaker beep on the 18th of every month every time you press a key. All you need to do is to get rid of the virus. This will usually take seconds or minutes.
2. Minor Damage.→ A good example of the minor damage is the way that the Jerusalem virus deletes any program that you try to run after the virus has gone memory resident on Friday the 13th. At worst, you will have to reinstall some programs, but repairing the damage is unlikely to take more than 30 minutes per computer. 
3. Moderate Damage.→  The most famous virus for moderate damage is Michelangelo. Moderate damage is done when a virus formats the hard disk, scrambles the File Allocation Table (FAT) or overwrites the hard disk. The damage is moderate only because you know that it has happened. You can reinstall DOS and reload yesterday's backup because you do take a backup every day. So, you will lose on the average half's a day's work, plus maybe an hour doing the reinstall and restore.
4. Major Damage.→ Every 16th time that a Dark Avenger- infected file is run, it overwrites a random sector on the hard disk with 'Eddie lives... somewhere.' Major damage is done when such virus infects your backups as well as your hard disk. This might have been going on for several weeks. When you find 'Eddie lives' at several places in several files you discover Dark Avenger, you get rid of the virus. You restore yesterday's backup and find 'Eddie lives' in the backup files. 

You might have to go back a few weeks before you can find clean data files. However, when you have restored a 6- week old backup, you will find that you do not actually have any way to redo the work you have lost because you do not have your original documents. 

5. Severe Damage.→ When a virus (e.g., Dark Avengers)  makes gradual, progressive changes so much that backups are also corrupted, but the changes are not obvious, so you end up simply not knowing whether your data is correct or changed. However, the virus might have done severe damage. 

6. Unlimited Damage.→  Some viruses make an effort to get to the system manager password and pass it to a third party. Cheeba virus creates a new user with maximum privilege with a fixed username and password. The third party person, who can log in to the system, can do anything and it turns can then do unlimited damage.

Virus Prevention 

We have discussed the damage done by viruses. The question now arrives how to prevent viruses from invading our computer systems. Various measures of virus prevention are:

1. Legislation
2. Awareness of users
3. Use of scanners 
4. Checksummers

Let us discuss these above things. 

1. Legislation

You should use only legal software to prevent your system from viruses. The government must punish people who write virus programs. This will reduce the number of viruses written by various authors. However, it cannot make an impact on the thousands of viruses that already exist through it can certainly slow down the creation of new viruses. 

2.  Awareness of Users

Users do not regard computer problems as their own. Users are too busy doing their jobs to pay any attention to looking out for viruses. Users can be precise procedures to follow, to check all incoming software and about how to acquire software. Procedures tell users how to obey the rules. The procedure for checking disks should be written down in detail.

However, most of the users just ignore procedures. A user may see a virus once in many years. Thus, after say six months of applying such procedures, they learn that when you go through the procedures, you do not find any viruses. So the procedure falls into disuse. The procedure can be backed up with some rules. A good set of rules might be as follows: 

•  Any incoming floppy disk must be virus-checked
•  If your anti-virus software finds a virus, tell your PC support department
•  If the rules are broken, users can be 'punished'.

Use of Scanners 

A scanner is a program that knows how to find a particular repertoire of viruses. Scanners are updated, quarterly or monthly. For many users, quarterly upgrades are sufficient, but every now and then, a new virus comes out and spreads very fast (for example, Tequila, or SMEG). In that case, you would be unable to detect this new virus for several weeks, depending on where you are in the update cycle. So you should subscribe to monthly upgrades to avoid this situation. 

Checksummers 

A checksummer is a change detector. Executable files should not change, except for a good reason like updating the software. A checksummer aims to detect changes. The advantage of checksummers is that they do not detect a repertoire of viruses, so do not need updating. The downside of checksumers is that they are more of a hassle than scanners because files change on your computer more often than you might have thought, for good and valid reasons. They also do not detect all viruses. For example, checksummer do not detect slow viruses, they do not detect all boot sector viruses (if the hard disk code is left unchanged) and they have problems with stealth viruses. 

THANKS, FRIENDS TO READ THIS POST

NEW TIPS FOR TECH