_ RU.LINUX (2:5077/15.22) ___________________________________________ RU.LINUX _
From : Eugene Fokin 2:5020/400 12 Apr 99 19:47:12
Subj : FTP modes: active and passive.
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From: Eugene Fokin <elf@solvo.spb.su>
Sergey Romanenko wrote:
....
5.2.3. FTP nightmares.
The classic packet filtering problem is FTP. FTP has two modes; the
traditional one is called active mode and the more recent one is
called passive mode. Web browsers usually default to passive mode,
but command-line ftp programs usually default to active mode.
In active mode, when the remote end wants to send a file (or even the
results of an ls or dir command) it tries to open a TCP connection to
the local machine. This means you can't filter out these TCP
connections without breaking active FTP.
....
Vova
