1 Oct 2007 17:50
RE: SSH connection attempts in logs.
Dan Denton <ddenton <at> remitpro.com>
2007-10-01 15:50:04 GMT
2007-10-01 15:50:04 GMT
I would suggest the OP look into something like denyhosts or sshdblock. These programs can block brute force attempts and are pretty customizable, and can blacklist any machine attempting to connect too many times using hosts.allow and hosts.deny. Sshdblock is a little easier to configure, but both are effective. -----Original Message----- From: listbounce <at> securityfocus.com [mailto:listbounce <at> securityfocus.com] On Behalf Of jason Sent: Sunday, September 30, 2007 8:02 PM To: security-basics <at> securityfocus.com Subject: Re: SSH connection attempts in logs. I have encountered similar issues and chances are, if you do not know who is trying to connect to you, safer to block first and respond later. If a an 'admin' or a 'staff' member is idiotic enough to screw it up more then 3 times, they need a lesson in security and whatnot. after a good row, I sincerely doubt they will login erroneously too often. At that point, no harm no foul. Honestly. As an administrator of an SSH running machine, if you don't recognize an IP or even the range that it's coming from, what choice do you have but to block it? Even if you do recognize the range and there are multiple failures? See previous response. Why would you need a secure shell if you didn't care who was connecting to your boxen? What I typically do to circumvent the default for scanners and similar ilk is to just change the port that ssh is on or to forward from the firewall a specific port. I have also seen mention of 'knock' style programs but have not had the spare time to implement a working 'knock' setup. At that point what do you care (for the most part) is hitting port 22? This just falls under basic security steps though and I am guessing is far from new information. Jason Tarbet Computer Nerd Bangor Humane Society ChromeSilver wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Dan Denton schrieb: > >> Well, I wouldn't lean toward anything that tries to connect on port 22 as >> noise. I would verify that the src IP address isn't some legitimate attempt >> to connect by an application that is simply misconfigured. If it's not >> legit, block it. In that case it's most likely an attack, or it could be a >> port scanner. Just my two cents. >> > > >> xxx.xxx.xxx.xxx = them >> yyy.yyy.yyy.yyy = me >> >> c=262144 m=98 msg="Connection Opened" n=187596 >> src=xxx.xxx.xxx.xxx:32881:X1 dst=yyy.yyy.yyy.yyy:22:X1 proto=tcp/22 >> c=1024 m=537 msg="Connection Closed" n=139129 >> src=xxx.xxx.xxx.xxx:32881:X1 dst=yyy.yyy.yyy.yyy:0:X1 proto=tcp/0 >> > > Yep, > > that's my guess too. It's some kind of port scanner very likely. Since > it isn't probing weak accounts (like root /w empty pw), so it cant be a > vuln scanner. But I wouldn't suggest blocking that IP, it could be a > dial-up conn. Better do a whois on that IP and then tell the ISP that > you're most likely being scanned from it. Then you could, eg. contact > that person via snailmail and let it know that there's an aware admin > online... > > Grz, > ChromeSilver > > - -- > "If light be the brightest light... > Wherfore then doth it shadows cast?" > - -R.Rohonyi > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.7 (MingW32) > > iD8DBQFG+0FCDZBprASGxfQRAmZ5AKCUOfJqIrxhlAUkrpfrMdNOHe0X+wCeL8oE > +NQu5JZ+eKqnQMlw8ZkPHvE= > =46vA > -----END PGP SIGNATURE----- > > >