Open an attachment? Help! What the heck is meant by that? For all these years, I never clearly understood just what was meant by open an attachment. I don't

Open an attachment? Help! What the heck is meant by that? For all these years, I never clearly understood just what was meant by open an attachment. I don't have a clear description, definition, or explanation. Help! [No joke] Background. In about 1995, I was using some OS/2 e-mail program that wanted to put an icon somewhere for each e-mail message, screamed bloody murder at all those absurd icons until my throat was sore, got out the e-mail RFCs, and in about an hour used the TCP/IP interface of the scripting language Rexx to write my own POP3 e-mail software. Did all the e-mail reading and writing in just my favorite text editor, KEdit. The pair worked great -- used them for years. Then, sure, just as in the e-mail RFCs, especially about multi-media internet mail extensions (MIME) or some such, there were attachments. So, again in Rexx, I wrote the basic base 64 en/decode software to handle attachments. So, of course, I could receive a virus via e-mail totally safely -- to me, an attachment was just some simple ASCII characters to be interpreted as the base 64 encoding of something, maybe a JPG file. No harm in receiving the ASCII characters -- they look like just gibberish of simple typing by a very busy kitty cat walking on a keyboard, no harm in that -- or the base 64 code or translating that base 64 code to bytes and storing the bytes in a disk file. A file is just a sequence of bytes, any bytes at all -- harmless. Simple. Save. So, if an attachment claimed that it was a JPG, then I might give the corresponding file from translation from base 64 to some graphic software to display the JPG. If in fact the attachment was an EXE to do harm to my computer data, etc., then I would trust the graphics program to notice that the attachment was not a JPG -- should be easy enough for the graphics program to tell. Then I moved to Windows XP and then SP3 and Outlook 2003, and I'm still there and see little or no reason to change but just want to get on with my real work where XP SP3 is fine. So, Outlook has attachments. Still, I never knew just what the heck was meant by open an attachment. So, if an attachment, say, in some MIME e-mail header line or some such, claims that it is a JPG file, then maybe give the attachment, translated from base 64, to some graphics program and trust that the graphics program will (1) display a real JPG without harm or (2) give an error message at anything else. Similarly for PNG, GIF, BMP, HTML, CSS, JS, etc. For an EXE, of course, certainly, no way would Windows let the thing try to execute as software, right? I mean, not a chance, true? Or, the old, rock solid, first rule of computer security was to never, but never permit data from an untrusted source to execute as software, right? Handle such data just as bytes, sure, okay, safe, etc., but just no way ever let it execute as software, and that should be okay, right? So, what does open do that is not safe? No joke: In all these years, I've heard about e-mail and open an attachment and still have no clear description, definition, or explanation that would say just what open does or why it's dangerous. As far as I can tell, the people, maybe who wrote Outlook 2003, who talked about doing an open on an e-mail attachment never really made at all clear just what the heck they were talking about. Since many people still are afraid of open, where I see little chance of harm, maybe others would like some clarity, too. Help! [no joke].