If you do discover how to do this reliably, I'd be interested in your solution. If you/someone else feels it's too unrelated to this list, feel free to email me directly, but I think this is generally interesting.
Ron Scott-Adams r...@tohuw.net "The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is." (Winston Churchill) On Jun 6, 2013, at 13:37 , Chris Knadle <chris.kna...@coredump.us> wrote: > On Thursday, June 06, 2013 13:18:39, Bernhard R. Link wrote: >> * Chris Knadle <chris.kna...@coredump.us> [130606 14:53]: >>> I'm glad you asked this, because it prompted me to investigate further. >>> This was something I was told was commonly done, but it looks now like >>> it might be a misnomer. I'm not able to find a concrete example of a >>> system that allows SMTP MTA transfers but doesn't allow telnet to the >>> SMTP port. [The instances that seemed to fit the symptoms look like >>> they have more "normal" root causes, such as ISP port 25 filtering.] >>> >>> Because I had repeatedly been told that telnet to the MTA was a security >>> problem, prior to now I had suspected that blocking telnet to SMTP might >>> be possible via firewall filtering that distinguished the "type of >>> service" somehow, but after doing some packet sniffing and examining the >>> resulting packet internals I'm starting to doubt this is possible. >> >> Actually, it is possible to block telnet (and I've seen some ISPs do it). > > Okay. I'm going to try to figure out how this is done, as this has been one > of those things "in the back of my mind" for a bit too long. > >> In unrelated news, using telnet is a bad idea. If you want to connect to >> some port and see what you get, use netcat. > > Yep, netcat looks like the better tool for this. Thanks for the hint! > > -- Chris > > -- > Chris Knadle > chris.kna...@coredump.us > GPG Key: 4096R/0x1E759A726A9FDD74 > > > -- > To UNSUBSCRIBE, email to debian-devel-requ...@lists.debian.org > with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org > Archive: http://lists.debian.org/201306061337.55807.chris.kna...@coredump.us > -- To UNSUBSCRIBE, email to debian-devel-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/928757f7-fe35-43bd-a784-1c83ac755...@tohuw.net
