nanog mailing list archives
Re: Computer systems blamed for feeble hurricane response?
From: Mike Tancsa <mike () sentex net>
Date: Tue, 13 Sep 2005 16:15:29 -0400
At 03:50 PM 13/09/2005, Joseph S D Yao wrote:
Oh, and also ... please consider that some firewalls try to discern whether the connection on port 25 is from a mail server or from Telnet. While I mourn the simplicity of manual debugging of such sites, it remains that: the fact that you can't TELNET HOST.DOMAIN 25 doesn't mean that there's no mail service there.
Making a network connection using the application "telnet" vs the application "sendmail" (or whatever MTA one uses) seems to be the same when doing a tcpdump on the data. I am not sure how a firewall would know -- purely at the network layer -- what the other side's application was/is that initiated the connection. Yes, the other end could try and connect back to the host, but there is no 2 way traffic as the 3way handshake is not completing and I dont see any other traffic coming back from that host attempting to discern any info.
---Mike
Current thread:
- Re: Computer systems blamed for feeble hurricane response?, (continued)
- Re: Computer systems blamed for feeble hurricane response? Steven Champeon (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Mike Tancsa (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? william(at)elan.net (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Steven M. Bellovin (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Christian Kuhtz (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? John Kinsella (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Suresh Ramasubramanian (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? william(at)elan.net (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Larry Smith (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Joseph S D Yao (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Mike Tancsa (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Joseph S D Yao (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Steven M. Bellovin (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Joseph S D Yao (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Joseph S D Yao (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Joseph S D Yao (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Steven M. Bellovin (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Joseph S D Yao (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Eric A. Hall (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Steven M. Bellovin (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? William Allen Simpson (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Valdis . Kletnieks (Sep 13)