What is a Virus?
- It must execute itself. It will often place its own code in the path of execution of another program.
- It must replicate itself. For example, it may replace other executable files with a copy of the virus infected file. Viruses can infect desktop computers and network servers alike.
Some viruses are programmed to damage the computer by damaging programs, deleting files, or reformatting the hard disk. Others are not designed to do any damage, but simply to replicate themselves and make their presence known by presenting text, video, and audio messages. Even these benign viruses can create problems for the computer user.
They typically take up computer memory used by legitimate programs. As a result, they often cause erratic behavior and can result in system crashes. In addition, many viruses are bug-ridden, and these bugs may lead to system crashes and data loss.
There a five recognized types of viruses:
- File infector viruses: File infector viruses infect program files.
- Boot sector viruses: Boot sector viruses infect the system area of a disk
- Master boot record viruses: Master boot record viruses are memory resident viruses that infect disks in the same manner as boot sector viruses.
- Multi-partite viruses: Multi-partite (also known as polypartite) viruses infect both boot records and program files.
- Macro viruses: These types of viruses infect data files. They are the most common and have cost corporations the most money and time trying to repair.
What is a Trojan horse?
Trojan Horses are impostors--files that claim to be something desirable but, in fact, are malicious. A very important distinction from true viruses is that they do not replicate themselves, as viruses do. Trojans contain malicious code, that, when triggered, cause loss, or even theft, of data. In order for a Trojan Horse to spread, you must, in effect, invite these programs onto your computers--for example, by opening an email attachment. The PWSteal.Trojan is a Trojan.
What is a Worm?
Worms are programs that replicate themselves from system to system without the use of a host file. This is in contrast to viruses, which requires the spreading of an infected host file. Although worms generally exist inside of other files, often Word or Excel documents, there is a difference between how worms and viruses use the host file. Usually the worm will release a document that already has the "worm" macro inside the document. The entire document will travel from computer to computer, so the entire document should be considered the worm. PrettyPark.Worm is a particularly prevalent example.
What is a Virus Hoax?
Virus hoaxes are messages, almost always sent by email, that amount to little more than chain letters. Some of the common phrases used in these hoaxes are:
- If you receive an email titled [email virus hoax name here], do not open it!
- Delete it immediately!
- It contains the [hoax name] virus.
- It will delete everything on your hard drive and [extreme and improbable danger specified here].
- This virus was announced today by [reputable organization name here].
- Forward this warning to everyone you know!
Most virus hoax warnings do not deviate far from this pattern. If you are unsure if a virus warning is legitimate or a hoax, visit the Security Response Hoaxes Web site.
What is not a Virus?
Because of the publicity that viruses have received, it is easy to blame any computer problem on a virus. The following are not likely to be caused by a virus or other malicious code:
- Hardware problems. There are no viruses that can physically damage computer hardware, such as chips, boards, and monitors.
- The computer beeps at startup with no screen display. This is usually caused by a hardware problem during the boot process. Consult your computer documentation for the meaning of the beep codes.
- The computer does not register 640 K of conventional memory. This can be a sign of a virus, but it is not conclusive. Some hardware drivers such as those for the monitor or SCSI card can use some of this memory. Consult with your computer manufacturer or hardware vendor to determine if this is the case.
- You have two antivirus programs installed and one of them reports a virus. While this could be a virus, it can also be caused by one antivirus program detect the other program's signatures in memory. For additional information, see Should you run more than one antivirus program at the same time?
- You are using Microsoft Word and Word warns you that a document contains a macro. This does not mean that the macro is a virus.
- You are not able to open a particular document. This is not necessarily an indication of a virus. Try opening another document or a backup of the document in question. If other documents open correctly, the document may be damaged.
- The label on a hard drive has changed. Every disk is allowed to have a label. You can assign a label to a disk by using the DOS Label command of from within Windows.
What can I do to prevent being infected by Virus?
- Do not open any files attached to an email from an unknown, suspicious or untrustworthy source.
- Do not open any files attached to an email unless you know what it is, even if it appears to come from a dear friend or someone you know. Some viruses can replicate themselves and spread through email. Better be safe than sorry and confirm that they really sent it.
- Do not open any files attached to an email if the subject line is questionable or unexpected. If the need to do so is there always save the file to your hard drive before doing so.
- Delete chain emails and junk email. Do not forward or reply to any to them. These types of email are considered spam, which is unsolicited, intrusive mail that clogs up the network.
- Do not download any files from strangers.
- Exercise caution when downloading files from the Internet. Ensure that the source is a legitimate and reputable one. Verify that an anti-virus program checks the files on the download site. If you're uncertain, don't download the file at all or download the file to a floppy and test it with your own anti-virus software.
- Update your anti-virus software regularly. Over 500 viruses are discovered each month, so you'll want to be protected. These updates should be at the least the products virus signature files. The McAfee Viruscan program installed on your PC is configured to automatically download the latest viruscan updates. To check if your Viruscan program is correctly configured to do this, review the configuration notes for Configuring Automatic Updates - VirusScan (For Laucala Campus).
- Back up your files on a regular basis. If a virus destroys your files, at least you can replace them with your back-up copy. You should store your backup copy in a separate location from your work files, one that is preferably not on your computer.
- When in doubt, always err on the side of caution and do not open, download, or execute any files or email attachments. Not executing is the more important of these caveats. Check with your product vendors for updates which include those for your operating system web browser, and email. One example is the security site section of Microsoft located at http://www.microsoft.com/security.
- If you are in doubt about any potential virus-related situation you find yourself in, you may report a virus to our virus team.
What is Safe Computing?
With all the hype, it is easy to believe that viruses lurk in every file, every email, every Web site. However, a few basic precautions can minimize your risk of infection. Practice safe computing and encourage everyone you know to do so as well.
- Do not leave a floppy disk in the floppy disk drive when you shut down or restart the computer.
- Write-protect your floppy disks after you have finished writing to them.
- Be suspicious of email attachments from unknown sources.
- Verify that attachments have been sent by the author of the email. Newer viruses can send email messages that appear to be from people you know.
- Do not set your email program to "auto-run" attachments.
- Obtain all Microsoft security updates.
- Back up your data frequently. Keep the (write protected) media in a safe place--preferably in a different location than your computer.
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