Re: Virus for 83

To: CALC-TI@LISTS.PPP.TI.COM
Subject: Re: Virus for 83
From: Reinier Zwitserloot <R.Zwitserloot@BTINTERNET.COM>
Date: Sat, 20 Sep 1997 16:11:28 GMT
Organization: BT Internet
References: <34231353.ED2054CF@geocities.com> <342381eb.1078474@news.btinternet.com> <3423d926.4376774@netnews.voicenet.com>
Reply-To: Reinier Zwitserloot <R.Zwitserloot@BTINTERNET.COM>
Xref: paladin.american.edu bit.listserv.calc-ti:16908

you can't attach in front- not without some extra tricks.
you'd have to overwrite (not attach, overwrite) the first 3 bytes of
actual code with a JMP to the very end. that very end replaces the
first 2 bytes of code with what it originally contained, then run
whatever your virus has to do (ie: crash the calc 5% chance). then
jump back to the start. problem with that is.. once you have
overwritten the first 2 bytes of code again, running it a second time
WONT call your virus code anymore. on IBM PCs this isn't a problem,
since the memory is reloaded from the .COM file, but you are going to
have to find another way (probably is none) to pull this off on the
TI-8x. Attaching it at the front will cause the memory referencing to
be screwed up.

References:

Virus for 83

From: Erik Soballe <webtoad@geocities.com>

Re: Virus for 83

From: Reinier Zwitserloot <R.Zwitserloot@BTINTERNET.COM>

Re: Virus for 83

From: Richard <jeffreyd@voicenet.com>

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