On Sat, 23 Oct 1999, [EMAIL PROTECTED] wrote:
> If sending "+ + + A T H 0" in an e-mail message (without quotes and spaces)
> hangs up the modem (or does it?), what about receiving? Suppose somebody sends
> you such a message from a LAN connection? Such a sequence could occur in a
> base64-encoded message as well as a plain-text file. Suppose such a string
> occurs in a file being uploaded or downloaded by FTP, or on a Web page?
Modems are supposed to have a guard time either side of the + + + such
that it is only recognized if no characters are received by the modem (via
its serial port) for some period of time before and after the + + +. But
some modems don't implement the guard time and if you have such a modem,
you would be vulnerable if you sent anything containing such a string. In
that case you could use the `escape 2b' option to pppd to make it turn all
+ characters into 0x7d, 0x0b sequences.
As for receiving, the modem certainly shouldn't be looking for the + + + in
the data received from the other modem, and I've never heard of any modem
that does.
Paul.
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