>>> Part 1 of 2...
 -=> Quoting Edward Tushar to All <=-
 ET> I am very novice when it comes to how viruses activate.  I have a
 ET> question - 
 ET> Can a virus be activated by viewing a JPG file?  I know it sounds
 
 Not to my knowledge.  However, the viewer program itself could be
 a virus dropper and when you run the program the virus could get
 loaded or copied to other files.
 
 ET> dumb, but when I was viewing a JPG file I downloaded from a 
 ET> BBS, the computer locked up after the picture was finished.
 ET> I turned off the power, waited 30 seconds and turned the system
 ET> back on.  I went to start up the graphic program and recieved a
 ET> stack overflow error.  I
 
 That could be a bug in the program itself, or a machine malfunction
 such as memory.  What type of CPU does it have?  I have run into
 several 386SX's that were bad about that, as well as some XT's.
 
 ET> rebooted the system again and the same thing happened.  I ran
 ET> SCAN and when I went to use edit to look at the log, I received
 ET> another error and the computer locked up.  (After scan completed
 ET> showing no
 
 Yeah, I ran into this with a couple machines where there was 
 something wrong with the machine.  I remember one 386SX in
 particular where it locked up every other time you ran edit.
 
 ET> viruses..)  Anyhow, is it possible? 
     Here is how I understand viruses to operate.  First of how you
 somehow pick up a virus.  This is typically through either trying
 to boot the machine from an infected diskette, or from running
 a program that is a virus dropper.  Then the "virus" code loads
 into memory, usually unannounced, and finds some way to spread
 itself.  It may copy itself to executable files or to the boot
 sector of the hard drive or to diskettes being accessed.  Then
 when you start the machine back up, the boot sector or some
 application you use will reload the virus.  Then if the infected
 programs are passed around and executed by someone else, or an
 infected boot sector is passed around on a diskette when is then
 left in the A: drive and someone forgets to take it out (if they
 didn't disable "boot from A:" in CMOS), then the whole process
 as mentioned here repeats itself on another machine.  That is
 just the delivery mechanism.  Usually viruses do more than just
 spread themselves around.  Hypothetically speaking only, I mean,
 if you go through all this trouble to write something like that, 
 then you would want some kind of credit, or maybe you wrote it 
 for revenge.  For example, most crooks, if they are going to
 break into a place, they are going to do something else like
 rob the place, vandalize it, kill someone, or burn it down.  So,
 usually, a virus is going to do other stuff.  Oftentimes, it
 waits for a specific trigger such as a certain word being typed,
 a certain time, a certain date, etc.  That is similar to tactics
 that terrorists use.  They usually do their bombings at times
 that they are the most likely able to prove their point, such
 as do it on a holiday that they don't agree with, or do it when
 the location is busy.  So someone could write viruses that only
 do damage during the tax season.  There are viruses that only
 cause damage on Sundays, and ones that only do it in the evening.
 I guess the reasoning is to catch the people who work late hours
 and weekends.  After the trigger is reached, whether it is a
 time, date, a word typed, a system interrupt, a disk access, or
 whatever, then something usually happens.  It could be to simply
 print garbage on the screen (or print cuss words or make letters
 "fall" off the screen), or to erase files, trash the FAT tables,
 partially format a disk, or whatever.  If the damage is serious,
 a typical virus will make sure there is plenty of itself around
 before it does it.  If the purpose of the virus was to crash
 many machines, then it couldn't do that if it only was able to
 do one or two.  In that case the trigger could be the number of
 files trashed, or the number of trashed files that make it to a
 floppy.
      The above is only a loose description of how viruses work.
 It is general in nature and is not intended to be complete, and
 I did take some deliberate liberties with logic.  This is just
 to give a rough idea so people won't think you get them from a
 toilet, or by looking at pornos, or by merely reading e-mail, or
 like the woman who thought she got a computer virus from her brand
 new, unopened, uninstalled modem.  No part of the text is to be
 taken as be promoting or encouraging viruses.  The discussion
 above does not refer to special-case productive viruses.  An
 example of that would be on the biological level.  There is a
 genetically engineered variation of the common cold which can
 be used to heal certain lung diseases.  Likewise, there was a
 computer virus that one software company wrote to fix a serious
 bug in their program.  It looked for the affected program,
 patched it to remove the bug, maybe made a copy of itself to
 spread to one other machine or disk, and then deleted itself.
 Then after the date that the trajedy was to occur that the virus
 was to prevent, any remaining copies of that virus deleted 
 themselves.  But, the reason they did that was because the effects
 of that virus were less harmful than the effects of the bug in the
 >>> Continued to next message...
--- GEcho 1.11+
---------------