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Computer viruses and how to combat them


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Computer Viruses (see Disclaimer Notice)

What are computer viruses?
The term Virus actually covers a range of computer programs which end up running on a computer and carrying out a range of operations. The 3 main groups are listed below:-

Virus. Code written with the express intention of replicating itself. A virus attempts to spread from computer to computer by attaching itself to a host program. It may damage hardware, software, or data. Often spread as attachments in e-mail. You can see a list of the latest top 10 virus alerts and a list of the top ten virus hoaxes (appear or pretend to be viruses but are not and should be ignored)

Worm. Self-propagating malicious code that can automatically distribute itself from one computer to another through network connections. A worm can take harmful action, such as consuming network or local system resources.

Trojan Horse. A program that appears to be useful or harmless but that contains hidden code designed to exploit or damage the system on which it is run. Trojan horse programs are most commonly delivered to users through e-mail messages that misrepresent the program's purpose and function.

How can we combat viruses?
The easiest way to get infected is to open an infected e-mail attachment. So, what can you do to reduce the chances of getting infected.

1. Most important - get antivirus software but only run one antivurus product at a time. It will check your mail as it arrives and will remove attachments with viruses. It is also most important that you keep it up to date - I would recommend that you check for virus updates when you first go online each day, BEFORE you check your e-mail, and install them immediately. You could get an e-mail with a virus which came out the day before and so your antivirus software is already out of date. Free antivirus software is available and a one is AVG (look for the AVG Free Edition download or you can purchase version 7). It is also recommended that you get and use some anti spyware software. Free software is available to download (Spybot Search & Destroy) or better software is avialable for approx £20 - rated top by PC Pro (Spyware Doctor - there is a download so you won't need a CD delivered)

2. Do NOT open an attachment from anyone AT ALL unless you are expecting it or you know exactly what the attachment is. Read the text in the message - viruses usually come in e-mails with poor English and the content is vague. The message often says things like 'Here is the info you wanted', 'your message could not be sent - click the attachment to see why'. Be suspicious of everything - nobody should send unsolicited attachments unless there is a good description which is specific to you, not a generalisation. Any mail returned to you will NOT have an attachment with the return details. The attachments which are safe are those with extensions JPG and GIF (these are picture files). Attachments which are not safe are EXE, COM, PIF, SCR, VBS, JS, BAT, SHS and HTA. Microsoft Office files (DOC and XLS) can contain Macros (programs which run inside the application) which can also act like viruses.

3. Get a Firewall and install it. See the Firewall page for more information.

4. Do a virus scan regularly to ensure protection. If you haven't got any antivirus software you can do a virus scan or a security scan online at various sites including Symantec. Here you need to go to Security Response / Check for Security Risks / Security Scan to check the firewall or Virus Detection to scan for viruses. If you have a known virus and want to remove it you can go to Symantec and then to Support / Downloads / Virus Removal Tools and select the relevant tool or you can get a Multipurpose Virus Remover Tool from AVG.

5. Keep Windows up to date. As viruses find new ways to exploit the operating system Microsoft provide patches to fix them and keeping up to date helps to reduce the vulnerability of Windows.

6. Turn on displaying file extensions - this is normally turned off in Windows. The file extension (the .jpg at the end of a filename) tells you what sort of file it is and what program it uses. It is possible to have more than one file extension so the file mypicture.jpg.exe is an executable (a program that can run on the computer). If you have file extension turned off then if you received it as an attachment it would be displayed as mypicture.jpg. You would assume it was a picture and open it which would infect your computer. How to turn it on depends on your operating system:-

Windows 95/ 98 - Click Start / Programs / Windows Explorer. Click View menu and select 'Folder Options'. Click 'View' tab and remove the tick for 'Hide extension for known file types'. Click the 'Apply' button and click the 'OK' button.
Windows XP - Click Start / Control Panel / Folder Options. Click View tab and remove the tick for 'Hide extension for known file types'. Click the 'Apply' button and click the 'OK' button.

How do viruses work?
If you find that you can no longer update your antivirus software then you may have already been infected. Some viruses can stop you accessing the antivirus web sites. You may need to get someone else to download the Virus Removal Tool onto a floppy disc so that you can remove the virus (read the instructions first though).

Most infected e-mails use address spoofing which works like this. The virus gets an e-mail address from the address book which becomes the To address. It gets another e-mail address which becomes the From address. So when you receive an infected e-mail it will almost certainly not be from the displayed sender. It will most likely be from someone who has both the To and From address in their address book. It is possible to discover the sender by taking information from the hidden content and informing the Internet Provider but this is a last step if you are being inundated with viruses. I last used it when I received 1,000 virus mails from one person in 1 week. I got them stopped within 24 hours.

Apple Mac users
OK - so what about Mac users. Home Mac users account for less than 1% of the total computers in use. Mac use is currently around 8% of which the vast majority is for business use in the graphics industry. As a result the risk from viral infection and outsiders gaining access to Macs is greatly reduced and, with care, should be almost non-existant.

Final advice
Be vigilant, don't trust anything, be careful what you download (OK from reputable sites). They are out there trying to trick you into giving them your personal data, bank account details or just e-mail addresses. Call your bank, your friends and work colleagues first if you are not sure.
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