mga boss…share ko lang po ito sa lahat..mga napulot ko kanina habang nagre-research ako tungkol sa mga computer virus at sa pagtanggal ng virus…..
A common misuse of the term viruses lately has been to refer to adware or spyware programs. However, computer viruses are malicious programs which are created with the sole intent of
disrupting the operation of a computer. Computer viruses are usually placed into computers without the permission or knowledge of the person who owns the computer, and can copy spread from one computer to another through the internet, CD’s, USB drives, floppies, messenger, or email.. A computer virus can cripple an entire computer system, damage files, or cause some minor or major annoyance problems to the computer owner.
Many people will install anti-virus software to help proactively detect and eliminate known infections, either when downloaded or executed. There are several ways these anti-virus programs work, but most commonly is using a list of signature definitions; comparing the content of the computer’s memory and hard drive files to a database of known ‘signatures’. Although effective at removing and preventing damage from viruses which are already known, they are only as strong as their most recent definition update. The other method to use a mathematical algorithm to locate suspected activity based on common behaviors. This method allows newer software to detect new, undefined ones.
Viruses aren’t new. The first virus appeared on ARPANET back in the early 1970′s, infecting the TENEX operating system, making use of any connected modem to infect other systems. The first ‘in the wild’ virus was written back in 1982 for the Apple operating system. This was originally intended as a joke, attached to a game, which on the 50th play would then infect the user’s system. The first boot sector viruses started in the 80′s, and continued to proliferate into the wild through BBS’s and software sharing. Some viruses were written by software programmers themselves to thwart off software pirating with infecting systems. The 90′s brought us macro viruses which spread through popular office suites. Newer types of viruses focus on replication through instant messaging and advanced hiding techniques.
This is a list of some of the more popular versions of computer viruses:
Boot Sector Computer Viruses
The boot sector viruses become a whole lot popular in the eighties. This was when computer technology actually hit the mainstream. Quite like the name, boot sector viruses infect the boot sectors of a computer. These boot sectors are usually located in the bootable disk or in particular location in your computer hard drive. A number of these boot sector viruses in the past include names such as Disk Killer and others like Michelangelo. The damage caused by boot sector viruses can be devastating, varying from individual file loss to entire directories.
Companion Viruses
These sorts of viruses usually affect your computer by infecting your computers operating system. They work by creating a dangerous program that looks like the other valid files that are on your computer. These programs accompany other files that exist on your computer, so you may end up executing a virus instead of the program that you really wanted to run. These types of viruses can wait in memory for a program to run and can easily replicate.
Email Viruses
These sorts of viruses use e-mail in order to transmit viruses from one computer to the other. Someone may send you an e-mail that has an attachment that has a virus in it. When you open the attachment your computer gets infected. Some of them actually copy themselves to all the e-mail addresses in your address book and the virus gets to spread as quickly as it can. Avoid opening e-mails from anyone that you don’t know. Some e-mail programs actually now come with the capability to scan through attachments with antivirus programs. They can easily identify any virus programs before you would even spot them.
Macro Viruses
Macro viruses are small programs which can infect files created with certain applications, including word processing and spreadsheet office suites. These little programs can take advantage of the program’s built in macro programming tools to perform maliciously.
Polymorphic Viruses
Polymorphic viruses actually will hide themselves each time they infect a system, making it nearly impossible to be detected by anti-virus string or signature searches. Because these types of viruses encrypt or encode themselves differently every time, they are more difficult to detect and are able to easily replicate large numbers of new instances of themselves.
Trojan horse viruses
Trojan horse viruses are actually malware, they are usually thought of as viruses because of the amount of damage that they can do to your computer. These viruses are actually quite tricky; they appear as something as innocuous as a screensaver or game. When you install the program you end up with a virus on your system. The virus may then leave a backdoor for hackers to enter into your computer. When these hackers enter they can then proceed to steal personal information such bank account and credit card information, and even passwords.
Worm Viruses
Worm Viruses have the ability to easily and quickly duplicate themselves, occupying tremendous amounts of computer resources while it wreaks havoc on your computer and network.
If you want to protect yourself from computer viruses such as the types listed above. It is absolutely essential that you obtain the best protection software available. Money need not be an obstacle for effective protection; there are many high quality free programs available. It’s important to make sure your anti-virus software is as up to date as possible, as new infections are discovered each day. You may also want to invest in a firewall that helps prevent other people accessing your computer. Once a computer is infected with a virus, it is unsafe to keep using this system; it can damage files and send to your contacts through email. You should also make regular backups of your data and keep this unconnected to your system, to restore your files if necessary.
Darren Williger is an over-caffeinated, security oriented winemaking enthusiast who writes for ActiveDirectory.US, NetworkSecurity.WS, and SpywareTool.com
Article Source: http://EzineArticles.com/?expert=Darren_Williger
Enlarge ImageComputer Virus is a kind of malicious software written intentionally to enter a computer without the user’s permission or knowledge, with an ability to replicate itself, thus continuing to spread. Some viruses do little but replicate others can cause severe harm or adversely effect program and performance of the system. A virus should never be assumed harmless and left on a system. Most common types of viruses are mentioned below:
Resident Viruses
This type of virus is a permanent which dwells in the RAM memory. From there it can overcome and interrupt all of the operations executed by the system: corrupting files and programs that are opened, closed, copied, renamed etc.
Examples include: Randex, CMJ, Meve, and MrKlunky.
Direct Action Viruses
The main purpose of this virus is to replicate and take action when it is executed. When a specific condition is met, the virus will go into action and infect files in the directory or folder that it is in and in directories that are specified in the AUTOEXEC.BAT file PATH. This batch file is always located in the root directory of the hard disk and carries out certain operations when the computer is booted.
Overwrite Viruses
Virus of this kind is characterized by the fact that it deletes the information contained in the files that it infects, rendering them partially or totally useless once they have been infected.
The only way to clean a file infected by an overwrite virus is to delete the file completely, thus losing the original content.
Examples of this virus include: Way, Trj.Reboot, Trivial.88.D.
Boot Virus
This type of virus affects the boot sector of a floppy or hard disk. This is a crucial part of a disk, in which information on the disk itself is stored together with a program that makes it possible to boot (start) the computer from the disk.
The best way of avoiding boot viruses is to ensure that floppy disks are write-protected and never start your computer with an unknown floppy disk in the disk drive.
Examples of boot viruses include: Polyboot.B, AntiEXE.
Macro Virus
Macro viruses infect files that are created using certain applications or programs that contain macros. These mini-programs make it possible to automate series of operations so that they are performed as a single action, thereby saving the user from having to carry them out one by one.
Examples of macro viruses: Relax, Melissa.A, Bablas, O97M/Y2K.
Directory Virus
Directory viruses change the paths that indicate the location of a file. By executing a program (file with the extension .EXE or .COM) which has been infected by a virus, you are unknowingly running the virus program, while the original file and program have been previously moved by the virus.
Once infected it becomes impossible to locate the original files.
Polymorphic Virus
Polymorphic viruses encrypt or encode themselves in a different way (using different algorithms and encryption keys) every time they infect a system.
This makes it impossible for anti-viruses to find them using string or signature searches (because they are different in each encryption) and also enables them to create a large number of copies of themselves.
Examples include: Elkern, Marburg, Satan Bug, and Tuareg.
File Infectors
This type of virus infects programs or executable files (files with an .EXE or .COM extension). When one of these programs is run, directly or indirectly, the virus is activated, producing the damaging effects it is programmed to carry out. The majority of existing viruses belong to this category, and can be classified depending on the actions that they carry out.
Companion Viruses
Companion viruses can be considered file infector viruses like resident or direct action types. They are known as companion viruses because once they get into the system they “accompany” the other files that already exist. In other words, in order to carry out their infection routines, companion viruses can wait in memory until a program is run (resident viruses) or act immediately by making copies of themselves (direct action viruses).
Some examples include: Stator, Asimov.1539, and Terrax.1069
FAT Virus
The file allocation table or FAT is the part of a disk used to connect information and is a vital part of the normal functioning of the computer.
This type of virus attack can be especially dangerous, by preventing access to certain sections of the disk where important files are stored. Damage caused can result in information losses from individual files or even entire directories.
Worms
A worm is a program very similar to a virus; it has the ability to self-replicate, and can lead to negative effects on your system and most importantly they are detected and eliminated by antiviruses.
Examples of worms include: PSWBugbear.B, Lovgate.F, Trile.C, Sobig.D, Mapson.
Trojans or Trojan Horses
Another unsavory breed of malicious code are Trojans or Trojan horses, which unlike viruses do not reproduce by infecting other files, nor do they self-replicate like worms.
Logic Bombs
They are not considered viruses because they do not replicate. They are not even programs in their own right but rather camouflaged segments of other programs.
Their objective is to destroy data on the computer once certain conditions have been met. Logic bombs go undetected until launched, and the results can be destructive. By Jayashree Pakhare
Published: 5/12/2007
Tips before downloading stuff from the internet.
The Internet contains vast amount of information and information such as ebooks and software can easily be obtained by downloading it into your computer. This will save time and effort and everything can also be automated. You can download the files even though you’re on a different time zone.
However, even though downloading files from the Internet have many advantages, there are some disadvantages because the files that you’ve downloaded maybe are malicious threats. Before downloading any files to your computer, I have six tips you should know so you can be more secure when downloading files from the Internet.
1. File Size
First of all, look at the file size of the files that you want to download. For example, you want to download freeware software from a web site and you know that the software file size should be around 12 or 13 MB. But on that web site, it says 234 kB. You need to be very careful with this as it might be a virus or trojan because the size is just not right.
Many people have been tricked to download this type of file and the files turn out to be malicious software.
2. Firewall
Use a firewall before downloading any files. If the files you’ve downloaded are trying to send privacy information to the hackers, it will not be able to do so because the firewall will block its outgoing traffic.
3. File Extension
File extensions is very important when downloading files from the Internet. File extension with .exe and have a small file size might be malicious software. It would be better you have an antivirus that will terminate the connection every time you tried to download any malicious software.
I have this one time when I was trying to download a files with .exe extension from the Internet without knowing it’s a trojan. My antivirus (I used Avast! at that time) terminate the connection immediately because it recognizes the file as a trojan. So, when you want to download any files, watch the extension. Files with double extension such as FILENAME.img.exe are mostly malicious software because it tries to trick you to think that it’s not malicious software.
4. Antivirus
As I told you from my story, I was saved from downloading malicious software by my antivirus and therefore, I strongly advise you to find an antivirus right now. If you don’t have any antivirus or anti-spyware programs on your computer, your computer might be infected.
5. Feedback
Websites such as download.com provide comment section or feedback for the download. Always read the download feedbacks before downloading because it will help you to know if the files are malicious software.
6. Internet Explorer Add-On
Use Internet Explorer Add-On that will tell you if the website you’re visiting contains threats that can affect your computer. Use add-on such as McAffe Site Advisor that you can download for free because this add-on will advise you which websites are safe to visit.
As I mentioned in the first tip, you need to know the file size before downloading. If you don’t know the file size, google it and visit the website which the site advisor add-on consider as safe.
There is no complete solution to computer security. The only way you can be sure your computer will be safe from any threats is by turning it off and sealed it in a sealed box. But what we can do is arm ourselves with essential security knowledge as it will help us in many ways.
Azwan Asmat is the author of Chuang Computer Tips – http://chuangcomputer.blogspot.com – Want to know the secret of securing your PC from dangerous spyware, adware, and malware programs that can ruin your PC, your finances, and your sanity?! Visit http://www.chuangcomputer.com/pcsafety/ for more info.
Article Source: http://EzineArticles.com/?expert=Azwan_Asmat
Posted in the different types of computer viruses...