RE: brute force attack - tcp wrappers and iptables not helping?

Hello,
Our company servers receive this kind of attacks every day, the things
that we've done and works ok for us are:
-Change the default port to a higher one like 3560, or something like
this.
-don't permit the root access.
-Create a user without a tipical name for the access, and after you can
su to the desired user.

This things don't stop the scans but it make very dificult to a standar
scan do something useful to the attacker.


El mar, 26-04-2005 a las 16:07, Susanne Hemker escribió:
> Hi everybody,
> thanks for your suggestions and sorry I did not get back to you
> earlier. 
> 1) I tried to ssh from a host that is not on in my /etc/hosts.allow and
> I do not get an ssh login, only : ssh_exchange_identification:
> Connection closed by remote host. 
> 2) The attacks come from different machines, some in Asia and some in
> the U.S., but those look to me as if they were hacked already in and are
> used to attack other computers. None of those IPs are in any way allowed
> to log onto my workstation. 
> 3) In the Iptables I have everything from the outside set to REJECT
> (both IPv4 and IPv6).
> 4) My "inside" hosts are on two subnets and those are listed in the
> /etc/hosts.allow and set to" ACCEPT all" in the Iptables
> 5) I do not have the hosts listed in the sshd_config, perhaps I should
> change this and also change the authentication method (which is
> PasswordAuthentication right now)
> Any further suggestions on how they might have gotten to the
> ssh-login?
> Thanks,
> Susanne
>  
> >>> [email protected] 04/22/05 9:38 AM >>>
> Susanne, I see your concern.  Properly configured IPTables rules and
> TCPWrappers should prevent this.  Have you actually attempted to
> access
> the ssh service from a host outside of the lab yourself?
> 
> Tim Walraven,CISSP,CISM,CISA
> Counterpane Internet Security
> 
> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]] On Behalf Of Susanne Hemker
> Sent: Thursday, April 21, 2005 10:24 AM
> To: [email protected] 
> Subject: [Intrusions] brute force attack - tcp wrappers and iptables
> nothelping?
> 
> Hi everybody,
> 
> somebody is trying to break into one of out workstations. 
> The /var/log/secure contains lots of:
> 
>  Failed password for invalid user $name  from ::ffff:$IP  port $port
> ssh2
> 
> from different IPs, ports and usernames.
> 
> Since the tcp wrappers and the iptables should not allow ssh login
> from
> 
> any host outside our lab, I am wondering how he/she even got to the 
> login. Any suggestions?
> 
> Thanks,
> 
> Susanne
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