Viruses

[Chuck Bearden]

Somebody please (please please!) correct me if I'm wrong, but I've been 
lead to believe the following about virus propagation:

1)  Boot sector viruses can't spread unless someone runs the executable
code in the boot sector by trying to boot from the disk in question
(whether or not it is bootable doesn't matter);  

2)  .exe and .com viruses can't spread unless someone runs the
infected executable code;

3)  Macro viruses can't spread unless someone opens a Word/Excel/etc.
file with a malicious macro in it, and runs the macro.  

Note that if 1) is true, one can't get a boot sector virus simply by
reading files from an infected floppy.  Boot sector code isn't
executed unless one actually tries to boot (I think).  


Am I wrong about any of these?  

If all the above propositions are correct, then an initially clean 
machine that has boot-to-floppy disabled, and that won't let users 
install or execute code they bring in, and that won't run document 
macros, is invulnerable to these three types of viruses.  

Chuck Bearden
Network Services Librarian
Houston Public Library
Houston, TX  77002
713/247-2264 (voice)
713/247-1182 (fax)
cbearden at hpl.lib.tx.us