The last few spam incidents I measured an outflow of about 2 messages per second. Does anyone know how aggressive Telnet and SSH scanning is? Even if it was greater, it's my guess there are many more hosts spewing spam
Sorry if I wasn't more clear, but I'm not asking about inbound attempts, I'm asking about the number of outbound attempts a host would perform. Frank -----Original Message----- From: Joel Jaeggli [mailto:joelja@bogus.com] Sent: Friday, March 07, 2008 11:41 PM To: frnkblk@iname.com Cc: 'Mark Foster'; Dave Pooser; nanog@merit.edu Subject: Re: Customer-facing ACLs Frank Bulk wrote: than
there are running abusive telnet and SSH scans.
Judging by the hits on my firewall there's a fair amount of variation between the scanners that are doing a couple login attempts per hour, and the bot that's making thousands of login attempts with 4 or 5 connection attempts going at a time. We don't filter them till they hit a threshold. I don't even bother to log telnet attempts anymore so I can't say much about that.
Frank
-----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Mark Foster Sent: Friday, March 07, 2008 10:02 PM To: Dave Pooser Cc: nanog@merit.edu Subject: Re: Customer-facing ACLs
Blocking port 25 outbound for dynamic users until they specifically request it be unblocked seems to me to meet the "no undue burden" test; so would port 22 and 23. Beyond that, I'd probably be hesitant until I either started getting a significant number of abuse reports about a certain flavor of traffic that I had reason to believe was used by only a tiny minority of my own users.
Sorry, I must've missed something. Port 25 outbound (excepting ISP SMTP server) seems entirely logical to me.
Port 22 outbound? And 23? Telnet and SSH _outbound_ cause that much of a concern? I can only assume it's to stop clients exploited boxen being used to anonymise further telnet/ssh attempts - but have to admit this discussion is the first i've heard of it being done 'en masse'.
It'd frustrate me if I jacked into a friends Internet in order to do some legitimate SSH based server administration, I imagine...
Is this not 'reaching' or is there a genuine benefit in blocking these ports as well?
Mark.