Buenos Días, Ignacio, Hay muchas formas para poder evitarlos: 1) Una es colocar un router con algún IDS, tipo Snort, ú otro para que la carga se haga en el router y no en el servidor DNS.- 2) Podes utilizar fail2ban, en otro hilo estamos discutiendo algo similar, te pego una de las posibles config que se puede hacer, esto es de uno de los foristas, para que te orientes:
había un problema similar con unos de mi vps, al revisar los logs full ataques, pero con pocas cosas los detuve, te explico a ver que te sirve:
1.- SSH: Cambie el puerto por Defecto.
2.- Definir Buenas Reglas Iptables y Shorewall (Administrar una Lista Negra de Ips de Ataques).
3.- Fail2ban: (Luego de Investigar mucho logre esta configuración):
[DEFAULT]
# "ignoreip" can be an IP address, a CIDR mask or a DNS host. Fail2ban will not # ban a host which matches an address in this list. Several addresses can be # defined using space separator. ignoreip = tu ip.
# "bantime" is the number of seconds that a host is banned. bantime = 36000
# A host is banned if it has generated "maxretry" during the last "findtime" # seconds. findtime = 600
# "maxretry" is the number of failures before a host get banned. maxretry = 3
# "backend" specifies the backend used to get files modification. # Available options are "pyinotify", "gamin", "polling" and "auto". # This option can be overridden in each jail as well. # # pyinotify: requires pyinotify (a file alteration monitor) to be installed. # If pyinotify is not installed, Fail2ban will use auto. # gamin: requires Gamin (a file alteration monitor) to be installed. # If Gamin is not installed, Fail2ban will use auto. # polling: uses a polling algorithm which does not require external libraries. # auto: will try to use the following backends, in order: # pyinotify, gamin, polling. backend = auto
# "usedns" specifies if jails should trust hostnames in logs, # warn when reverse DNS lookups are performed, or ignore all hostnames in logs # # yes: if a hostname is encountered, a reverse DNS lookup will be performed. # warn: if a hostname is encountered, a reverse DNS lookup will be performed, # but it will be logged as a warning. # no: if a hostname is encountered, will not be used for banning, # but it will be logged as info. usedns = warn
# This jail corresponds to the standard configuration in Fail2ban 0.6. # The mail-whois action send a notification e-mail with a whois request # in the body.
[ssh-iptables]
enabled = true filter = sshd action = iptables[name=SSH, port=ssh, protocol=tcp] sendmail-whois[name=SSH, dest=root, sender=tu email] logpath = /var/log/secure
[proftpd-iptables]
enabled = true filter = proftpd action = iptables[name=ProFTPD, port=ftp, protocol=tcp] sendmail-whois[name=ProFTPD, dest=tu email] logpath = /var/log/proftpd/access.log maxretry = 5
# This jail forces the backend to "polling".
[sasl-iptables]
enabled = true filter = sasl backend = polling action = iptables[name=sasl, port=smtp, protocol=tcp] sendmail-whois[name=sasl, dest=tu email] logpath = /var/log/maillog maxretry = 3
# Here we use TCP-Wrappers instead of Netfilter/Iptables. "ignoreregex" is # used to avoid banning the user "myuser".
[ssh-tcpwrapper]
enabled = true filter = sshd action = hostsdeny sendmail-whois[name=SSH, dest=tu email] ignoreregex = for myuser from logpath = /var/log/secure
# This jail demonstrates the use of wildcards in "logpath". # Moreover, it is possible to give other files on a new line.
[apache-tcpwrapper]
enabled = true filter = apache-auth action = hostsdeny logpath = /home/*/logs/*error.log /home/*/logs/error.log maxretry = 6
# The hosts.deny path can be defined with the "file" argument if it is # not in /etc.
[postfix-tcpwrapper]
enabled = true filter = postfix action = iptables-multiport[name=postfix, port="110,995,143,993,25", protocol=tcp] sendmail-buffered[name=BadBots, lines=5, dest=tu email] logpath = /var/log/maillog maxretry = 3
# Ban hosts which agent identifies spammer robots crawling the web # for email addresses. The mail outputs are buffered.
[dovecot]
enabled = true filter = dovecot action = iptables-multiport[name=Dovecot, port="110,995,143,993,25", protocol=tcp] sendmail-whois[name=Fail2Dovecot, lines=5, dest=tu email] logpath = /var/log/dovecot.log maxretry = 3
[apache-badbots]
enabled = true filter = apache-badbots action = iptables-multiport[name=BadBots, port="http,https"] sendmail-buffered[name=BadBots, lines=5, dest=tu email] logpath = /home/*/logs/access.log bantime = 172800 maxretry = 1
# Use shorewall instead of iptables.
[apache-shorewall]
enabled = true filter = apache-noscript action = shorewall sendmail[name=Postfix, dest=tu email] logpath = /home/*/logs/error.log
# This jail uses ipfw, the standard firewall on FreeBSD. The "ignoreip" # option is overridden in this jail. Moreover, the action "mail-whois" defines # the variable "name" which contains a comma using "". The characters '' are # valid too.
# This jail blocks TCP traffic for DNS requests.
[named-refused-tcp]
enabled = true filter = named-refused action = iptables-multiport[name=Named, port="domain,953", protocol=tcp] sendmail-whois[name=Named, dest=tu email] logpath = /var/log/messages ignoreip = tu ip
# Jail for more extended banning of persistent abusers # !!! WARNING !!! # Make sure that your loglevel specified in fail2ban.conf/.local # is not at DEBUG level -- which might then cause fail2ban to fall into # an infinite loop constantly feeding itself with non-informative lines [recidive]
enabled = true filter = recidive logpath = /var/log/fail2ban.log action = iptables-allports[name=recidive] sendmail-whois-lines[name=recidive, logpath=/var/log/fail2ban.log] bantime = 604800 ; 1 week findtime = 86400 ; 1 day maxretry = 5
Estas son algunas opciones que puedes configurar en tu fail2ban, si buscas en google con tus logs que ya tienes puedes probar cada una de ellas, te recomiendo que crees tu propio archivo jail.local en vez de jail.conf, asi cada vez que actualices tendrás tus reglas guardadas sin problemas, todo es cuestión de paciencia y sobre todo de analizar tus logs para detectar los ataques que recibes, claro habrán otros que no veras como escaneos,
Saludos
El 3 de octubre de 2013 10:22, Ignacio Ordeñana ifor1982@gmail.comescribió:
hola me gustaria saber como evitar ataque DDoS a mi servidor dns por medio de iptables e inclusive como volver mas seguros el servidor dns para evitar estos tipo de ataques
saludos _______________________________________________ CentOS-es mailing list CentOS-es@centos.org http://lists.centos.org/mailman/listinfo/centos-es