: : >>> Because under an operating system with protected memory, such as Unix or
: : >>> VMS, it is impossible for a virus to spread.
: Wrong, only unlikely, "today". See below.
: : Bob> Actually, as others have pointed out to me, it is possible for a virus
: : Bob> to spread on a UNIX machine. It is, however, difficult for a virus
: : Bob> to do anything very "useful" in a unix environment. An infected user
: : Bob> might lose all his files, a stupid administrator who runs downloaded
: : Bob> programs as root might even lose a complete system, but in the main,
: : Bob> Unix file system protections greatly limit a viruses scope.
: : Programs which operate as such are not viri. A computer virus is a program
: : that replicates itself, on its own, whether you want it to or not; that's
: : the definition of a virus. As none of these replicate themselves, they are
: : not viri. A trojan horse is something disguised as something else; hacked
: : system files such as ``ls'' or stuff pulled from the nets which do
: : unexpected things outside of their scope are trojan horses, not viri.
: : Bob> BTW, the OS's protected memory scheme protects users from each other,
: : Bob> it is not the mechanism that protects Unix from viruses.
: : Yes, it does. If a virus can't wedge itself into memory somewhere, it can't
: : replicate itself. If it can't replicate itself, it can't spread. Game over.
: If a program can infect another program, it has replicated itself. It
: is not necessary for a virus to be "wedged into memory". It is very
: possible (and even normal in the DOS world) for a program to make changes,
: add code, etc., to other executables in your local directory. It is even
: possible for such a program to check to see if it has privileges, and
: infect programs in the normal Unix locations: /bin, /usr/bin, /opt/bin,
: etc. It is also possible for an infected program to spawn a process that
: looks for "opportunities" in the running system to infect still other
: programs, or even other sytems in a networked environment. It is also
: possible for a trojan horse to carry the virus, and infect other executables
: it has read/write access to. So, whether or not you have a protected
: memory environment, you're vulnerable. If you don't have a secure system,
: you can be infected. It's also possible for an executable to be infected,
: and not do any damage until it's executed with privilege. Makes you
: think, doesn't it?
: BTW, a running process makes a pretty good substitute for being
: "wedged into memory somewhere", doesn't it?
: The game, as they say, is not quite over.
: If power corrupts, and absolute power corrupts absolutely,
: government corruption WILL be reduced by reducing government power. q.e.d.
: Bob Stewart (KB9ZW)
: wk USA (310) 335-7152
Brighton Health Care NHS Trust, UK
The ideas, suggestions, jokes, cautions, complaints, comments, scripts, insults,