Worms, trojan horses, macro viruses, boot sector viruses....it can be rather dangerous to be a computer user these days, especially if you share data with other people or download software from the Internet. The danger isn't exactly targeted towards you, but towards your data, which, in some cases, can be destroyed.
A virus is just a computer program. Like any other program, it contains instructions that tell your computer what to do. But unlike an application, a virus usually tells your computer to do something you don't want it to do, and it can usually spread itself to other files on your computer--and other people's computers.
A virus is a program or piece of code (computer instructions) that is loaded onto your computer without your knowledge and runs against your wishes. Viruses can be hidden in executable program files posted online, secreted in mail attachments or can be distributed in other ways.
If you're lucky, a virus will execute only a benign personality quirk, such as causing your computer to make seemingly random bleeps. But a virus can also be very destructive; it could format your hard drive, overwrite your hard drive boot sector, or delete files and render your machine inoperable.
Most viruses can also replicate themselves. They can spread swiftly across open networks such as the Internet, causing billions of dollars worth of damage in a short amount of time. All computer viruses are manmade. A simple virus that can make a copy of itself over and over again is relatively easy to produce. Even such a simple virus is dangerous because it will quickly use all available memory and bring the system to a halt. An even more dangerous type of virus is one capable of transmitting itself across networks and bypassing security systems.
Since 1987, when a virus infected ARPANET, a large network used by the Defense Department and many universities, many antivirus programs have become available. These programs periodically check your computer system for the best-known types of viruses
Some people distinguish between general viruses and worms. A worm is a special type of virus that can replicate itself and use memory, but cannot attach itself to other programs.
A Trojan horse is a destructive program that masquerades as a benign application. Unlike viruses, Trojan horses do not replicate themselves but they can be just as destructive. One of the most insidious types of Trojan horse is a program that claims to rid your computer of viruses but instead introduces viruses onto your computer.
The term comes from a story in Homer's Iliad, in which the Greeks give a giant wooden horse to their foes, the Trojans, supposedly as a peace offering. But after the Trojans drag the horse inside their city walls, Greek soldiers sneak out of the horse's hollow belly and open the city gates, allowing their fellow soldiers to pour in and capture Troy.
A macro virus is a type of computer virus that is encoded as a macro** embedded in a document. Many applications, such as Microsoft Word and Excel, support powerful macro languages. These applications allow you to embed a macro in a document, and have the macro execute each time the document is opened. According to some estimates, 75% of all viruses today are macro viruses. Once a macro virus gets onto your machine, it can embed itself in all future documents you create with the application. Antivirus programs can protect your system against most macro viruses, although new ones are always being created that slip by the antivirus filters.
**a macro is a symbol, name, or key that represents a list of commands, actions, or keystrokes. Many programs allow you to create macros so that you can enter a single character or word to perform a whole series of actions. You can also use macros to enter words or phrases that you use frequently. For example, you could define a macro to contain all the keystrokes necessary to begin a letter -- your name, address, and a code that inserts the current date. Then, whenever you write a letter, you just press the macro key to include the letter header.
Boot sector infecting viruses are one of the most common types of viruses around. A boot sector is a special location on all disks, hard or floppy, where the Basic In/Out System (BIOS) of a computer looks during the booting of a computer for a bootable system. The boot sector of a disk stores instructions that identify the partition on a disk, contains startup files, etc.Boot sector viruses put viral code (instructions) into the boot sector of a disk. When the computer is booted (turned on), the viral code is executed, putting the virus into memory and infecting the hard drive master boot sector.
Once infection of the master boot record of the hard disk occurs the virus is run in memory each time the computer is booted from the hard drive. All disks used on the computer from that point forth have their boot sector infected with the virus code. This leads to proliferation to other systems or reinfection of a cleaned computer at a later date.
There are ways to protect your computer from viruses. First, read this article to understand what viruses are and how they work. Second, equip your computer with a reliable anti-virus software program.
Anti-virus programs come with a database of information on thousands of known viruses. The program looks through all the data on your hard drive to see if anything matches a pattern in that database. Since new viruses are constantly appearing, you must update your anti-virus program regularly. Most anti-virus software publishers release updates to their software containing information on new viruses every few months. By downloading a small driver file used with the software, you'll have maximum protection against new viruses and Trojan Horse programs.
A Trojan Horse is a program that appears to perform a valid function but contains, hidden in its code, instructions that cause damage (sometimes severe) to your computer. Trojan Horse programs may compromise the security of an Internet account, contain objectionable graphics, or cause damage to your computer files.
Not all anti-virus software programs protect you from Trojan Horse programs. However, you can easily avoid Trojan Horse programs by NEVER downloading a file attached to an e-mail from someone you don't know. Some email providers, for example, America Online, helps you remember this with an automatic warning system. If you start to download a file type that is typically associated with Trojan Horse programs, you will receive a warning message. You may then decide to proceed with the download or cancel it. If you don't know the sender, don't download the file!
There are thousands of viruses in circulation. Here are some tips to protect your from infecting your computer:
* Don't Take E-mail from Strangers: Despite rumors you may have heard, you can't catch a virus by reading e-mail or participating in an Instant Messag conversation. You can, however, get a virus if you download an infected file attached to an e-mail message. Here's a simple rule: If you don't know the sender, don't download the attachment -- no matter how interesting it may appear to be.
* Watch the Net: Exercise caution if you download files from the Internet (either via the World Wide Web or FTP). Look for a statement at the site saying that its files have been checked by an anti-virus program. Downloading from a legitimate site that checks its files for viruses is likely to be safe. If the files haven't been checked, or if you're not sure, then either download the file to a floppy disk and check it with your own anti-virus software or don't download from that site at all.
* Spread the Word: Sure, you practice safe surfing, but what about the other members of your household? You can't watch your teenager every minute. Will the allure of a new program or game be more than they can stand? Will they download a file and then run it before scanning it with an anti-virus program? Share the information in this area with other members of your family and have a discussion about how to keep your computer safe from viruses.
* Check your Floppies: Another way viruses spread is by infecting floppy disks. If you bring work home from the office, you could bring a virus home, too. Scan all your floppies to make sure they're safe. (You might also consider e-mailing files to yourself at home instead of bringing them via floppy disk.)
* Back it Up: The best way to protect the data on your computer is to back it up on a regular basis. There are lots of back-up options available these days, from tape cartridges to special high capacity disks. If a virus slips through your defenses, a back-up will let you replace files destroyed by the infection.
* Stay Current: Because new viruses are being created all the time, you've got to keep your anti-virus software up to date. Look for updates containing information on new viruses from the software's publisher.
* Arm Your Computer: Of course, the best way to protect yourself against viruses is to be armed with potent anti-virus software.
1. Stop using the computer: You should never try to do normal work on an infected computer. Don't try to delete files you think may be infected -- it's unlikely that you'll get rid of the virus that way. If possible, exit all your programs and shut the computer down normally, don't just hit the "off" switch.
2. Don't use any floppy disks: Don't risk spreading the virus to someone else. Many viruses are transferred from computer-to- computer on floppy disks. Never put a floppy into a computer you think may be infected.
3. Confirm the presence of a virus, then get rid of it: Just because you're having a problem doesn't mean your computer has a virus. You may have a hardware problem. No matter what, run a virus-checking program to identify and remove any viruses. For an extra-added measure of security run two different programs -- anti-virus programs recognize different viruses and hunt viruses in different ways. Running two programs will help insure that the virus is removed.
4. Scan all floppy disks: If you've confirmed the presence of a virus, scan all your floppy disks with the anti-virus software to make sure they're not infected too. You wouldn't want to clear out the virus only to have a floppy re-infect your computer!
