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> Most famous in-band admin hack has to be the +++ syntax for Hayes modems which flipped the mode bit into 'command' mode serial comms mode. Unlike this case t
by praptak 14y ago
> Most famous in-band admin hack has to be the +++ syntax for Hayes modems which flipped the mode bit into 'command' mode serial comms mode.
Unlike this case the +++ hack did not really limit legitimate data you could send on Hayes. As far as I remember it had to be preceded and followed by pauses, so transmitting this comment wouldn't trigger it.
- ChuckMcM 14y agoYes, the pauses were essential to the patent. As I recall they had to be a specific length and a couple of knock offs worked around the patent by making them slightly shorter.
- danielweber 14y agoFrom what I recall (and this could very well be apocryphal), the pauses were what was patented. Non-Hayes modems still reacted to +++ but didn't need the pause. So if you could trick their software into sending "+++ATH;ATDT911" you would make them call 911. I'd love confirmation or denial of that patent thing.
- ChuckMcM 14y agoFrom the wikipedia page (so take it with a wikipedia sized grain of salt :-) "Hayes had patented this concept in 1985 in patent #4,549,302, the Modem With Improved Escape Sequence With Guard Time Mechanism, generally referred to as the "Hayes '302 patent". Hayes licensed the guard time to other manufacturers for $1 a modem – a charge which competitors derisively termed the "modem tax". A number of manufacturers banded together and introduced the Time Independent Escape Sequence, or TIES, but it was not as robust as Heatherington's system and never became very successful."