4 ms·

Okay, you're most likely trolling. Hexdump of this alleged virus or it didn't happen. Just to make sure, I tested this on MS-DOS 2.0 in an online emulator[1] f

Okay, you're most likely trolling. Hexdump of this alleged virus or it didn't happen. Just to make sure, I tested this on MS-DOS 2.0 in an online emulator[1] for a machine of the vintage you described, and it did exactly what I expected: A> echo>deadbeef.com A> dir deadbeef.com DEADBEEF.COM 12 A> type deadbeef.com ECHO is on A> deadbeef (starts spewing gibberish) COPY CON can't create an empty file either. Running an empty program (or falling off the end of this one containing the message from ECHO) will execute whatever happens to already be in memory at the time. Might work if there was another program loaded before, but not from a freshly booted system. The disk format is 5.25", not 5.4" Unexpected disk activity when the machine is idle would mean the virus also hooks the timer interrupt and does stuff in the background, instead of (or in addition to) infecting programs you actively run. Implementing that on an OS not designed for multitasking is certainly possible, but would take quite a bit more than 100 bytes of code. As for viruses of 76 bytes or less being common, AFAIK all of those are direct-action overwriting. Meaning that they don't stay active in the background, and any infected program will no longer work. Too simple and destructive to be viable. [1] https://www.pcjs.org/machines/pcx86/ibm/5160/cga https://www.pcjs.org/machines/pcx86/ibm/5160/cga edit: There is apparently a memory resident 76-byte virus, however note that it simply overwrites programs when they are copied, is "Rare", and was discovered in 1994, quite late for the machine you described: https://wiw.org/~meta/vsum/view.php?vir=1232 https://wiw.org/~meta/vsum/view.php?vir=1232 Most likely no copies of it exist outside of the "virus research" community.

helpfulContrib 3y ago
Oh p'schaw, you are the troll. Copy CON: can create an empty file, you just don't know how to do it. An 'empty program' such as a zero-byte .COM file created with COPY CON: is loaded into memory by DOS, and thus attackable by any virus set up with the suitable vector to do so. 5.25" was supposed to be typed 5¼", duh. Unexpected disk activity when the machine is idle would mean the virus also hooks the timer interrupt and does stuff in the background, instead of (or in addition to) infecting programs you actively run. Implementing that on an OS not designed for multitasking is certainly possible, but would take quite a bit more than 100 bytes of code. False. Read more virus code. I don't care for your conclusions, which are merely fallacious and ill-intentioned. The machine exists, as does the virus, and it'll be in a museum in a month or so, folks will play with it. That's all that matters to me. Your faith in your own knowledge doesn't impress me.

helpfulContrib 3y ago

Oh p'schaw, you are the troll. Copy CON: can create an empty file, you just don't know how to do it. An 'empty program' such as a zero-byte .COM file created with COPY CON: is loaded into memory by DOS, and thus attackable by any virus set up with the suitable vector to do so. 5.25" was supposed to be typed 5¼", duh. Unexpected disk activity when the machine is idle would mean the virus also hooks the timer interrupt and does stuff in the background, instead of (or in addition to) infecting programs you actively run. Implementing that on an OS not designed for multitasking is certainly possible, but would take quite a bit more than 100 bytes of code. False. Read more virus code. I don't care for your conclusions, which are merely fallacious and ill-intentioned. The machine exists, as does the virus, and it'll be in a museum in a month or so, folks will play with it. That's all that matters to me. Your faith in your own knowledge doesn't impress me.