Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!decwrl!ucbvax!pro-sol.cts.com!mdavis
From: mdavis@pro-sol.cts.com (Morgan Davis)
Newsgroups: comp.sys.apple
Subject: Re: A+ virus article
Message-ID: <8903141458.AA21538@crash.cts.com>
Date: 14 Mar 89 14:32:19 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: pnet01!pro-sol!mdavis@nosc.mil
Organization: The Internet
Lines: 27

Simply stated, an Applesoft BASIC program (BAS file) cannot be infected by a
propogating virus (at least none of the current strains) because only SYStem
applications are targetted.  So BAS files are safe from infection.

Now, (jeez) this doesn't mean that somebody cannot write a BASIC program that
pokes dangerous machine code into memory.  What the article stated was that
tokenized Applesoft files are safe from infection because the BASIC
interpreter in ROM only knows how to parse the tokens and execute the proper
subroutines that are burned into the Applesoft ROM code.  If, say, Festering
Hate were attached to the end of a BASIC program, you could "RUN" it without
any fear of catastrophe.  This also includes the old trick of appending
machine code to the end of a BASIC program.  Unless there is a command (CALL
whatever) in the BASIC program itself to jump-start that appended code, you're
safe.

Since BASIC programs include both their own source and runtime code, you're
advised to LIST any program you download to see if it does something nasty or
mysterious.  Besides, it doesn't take machine code and viruses to endanger
your computer.  All someone has to do is write a routine in Applesoft that
opens up your volume directory (good old "OPEN" and "READ" commands in BASIC)
and then proceed to delete your files with DELETE.

--Morgan Davis

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