Silicon Valley - Public Access Link

Protecting Yourself from Viruses

One of the most common ways for your computer to get infected by a computer virus is via e-mail. Other methods of infection include downloading infected software, or using an infected floppy disk. Your best protection against computer viruses is to obtain and install virus protection software and keep it up-to-date. Keeping the software up-to-date is important because virus protection software generally can only protect against known viruses. As new viruses are discovered the vendors update their software to detect these new viruses. Registered users can generally receive these updates via the Internet. Old virus software that is not maintained provides little protection.
The following information is provided to help users protect themselves from viruses. SVPAL cannot guarantee that the following information is completely accurate or will provide the necessary protection. Use this information as a guide only and always use common sense and due care.

If you do not have virus protection software installed, you can still take steps to protect yourself from viruses. Whenever you install software you should take care that the software is from a reputable source. There have been cases in the past where shrink-wrapped software from reputable sources has been infected, but such cases are very rare.

E-Mail Viruses

The primary source of virii today is from e-mail attachments. E-mail attachments are files that are transmitted as part of an e-mail message. These files can contain anything including virus-infected programs. Just downloading your e-mail cannot infect your computer. Even reading e-mail should not cause an infection by a virus. The danger lies in opening attachments contained in the e-mail. Most attachments are safe. These generally include Web pages, text files, images. 
Important caveat: a new class of virus is spreading that takes advantage of bugs in Outlook that automatic-ly open attachments when email is read. Opening the message is sufficient to launch these virii.

Some attachments try to pretend they are harmless by using a name like image.jpg.vbs. Note the final final suffix .vbs, which indicates a Visual Basic Script (a program). The .jpg in the name is there to trick the user into think that this an image file, but in reality it is a program, known as a Trojan horse. These usually carry a virus payload. You should always be suspicious of a file with a double extension.

Attachments Generally Safe to Open

Files with the following file suffixes are generally safe to open.  Don't be fooled by double extensions like picture.jpg.lnk.  This is a program and not an image.  The last part of the name, .lnk, determines the file's properties.  More recent viruses attempt to obfuscate the extra extension by including spaces (e.g. picture.jpg                        .exe) in the name. 
File Extensions File Type
jpg, jpe, jpeg, gif, tif, tiff, png Image Files
txt, html Text

Files Which may Contain Viruses

Files with the following file suffixes may contain macro viruses. If they are opened with macros disabled they MAY be safe to open.

File Extensions File Type
doc, dot MS Word Documents
xls, xlt MS Excel Spreadsheet

Files with the following suffixes are executable programs or script files. They may be infected with viruses. There is NO safe way to open these. Only open if necessary and if the source is trusted.

File Extensions File Type
exe, com, bas, pif, lnk Executable Programs
vbs, bat Executable Scripts
scr Screen Saver
class Java applets [1] & programs
ocx Active X [2]

[1]    Java applets loaded at part of a web page should be safe as the Java security system prevents these programs from misbehaving. 

[2]    Signed Active X plug-ins should be safe if signed by a reputable software provider.  These are often automatically downloaded as part of a web page.


[SVPAL Home] [Subscriber]

Contact Silicon Valley Public Access Link
Last Updated: Wednesday July 8, 2015