Image files do not get executed in anything like the way that .exe files
get executed.  They do not contain raw executable binary code; they contain
encodings of display bitmaps.
  A few experiments have involved storing virus binaries inside of image
files.  To actually activate such a virus, you need a malicious, infected,
or very seriously defective image "viewer" program, and nobody has been able
to spread such a beast to significant numbers of users.

  There is a persistent class of Windows security bugs in the code used by
Internet Explorer (and Outlook, etc) to render HTML pages.  If the page
includes a file of, say, type ".jpg", but the file doesn't have the normal
JPEG image headers, Microsoft's code will gladly try to recognize if the
file is of some other type that it knows how to deal with -- and this
happens after the decision that this file, as a JPEG, must be harmless....

  SO:  There are ways to embed viral code in image files, but they don't
"execute" in any meaningful sense without help.

Dave Gillett



On 19 Dec 2003 at 1:04, John Dent wrote:

> Sue & Dean,
>
> Actually any file can carry a virus as long as it is of adequate size to
> carry and hide the virus.  To activate a virus in an image file it is only
> necessary to double click on it. (Even though the file does not have a
> "*.exe" or other executable extension shown, it will execute!) Of course a
> file name with "*.exe" is more likely to be clicked on if it is thought to
> contain something that is wanted by the recipient. The best rule is be wary
> of all attachments.
>
> John
>
> At 10:49 AM 12/18/2003 -0500, you wrote:
> >Dean,
> >
> >I think you're thinking of a *.PIF file, not a *.GIF file.
> >To my knowledge, there has never been any virus attached to a
> >picture file.
> >For the Eudora problem,  is it possible that support for the .gif file
> >has been removed due to the copyright lawsuits involving
> >Compuserve and the format? Just a thought.
> >
> >Sue Clark
> >Bristol, ME
> >
> >On 17 Dec 2003 at 0:00, Dean Kiley wrote:
> >
> > > I do not use Eudora, but .gif is an extension that is well know as one
> > > that many times carries viruses, and therefore is blocked by many E Mail
> > > client software programs. You can defeat it in OE & Outlook by changing
> > > this preference in Options> Security, but is worded differently in these
> > > applications so you will need to hunt around for it.
> > >
> > > HTH
> > >
> > > Dean Kiley
> >
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