Postfix a way to limit the frequency of brute force?
In file /usr/local/etc/postfix/main.cf place something like the following:
Code:
...
# RATE THROTTLING
smtpd_client_connection_rate_limit = 20
smtpd_error_sleep_time = 10s
smtpd_soft_error_limit = 3
smtpd_hard_error_limit = 5
...
Install fail2ban or OSSEC for login error monitoring.
Mode info:
http://www.postfix.org/TUNING_README.html#conn_limit
How to block Spam before it enters the server
Open /etc/postfix/main.cf and place the following lines in it (replacing the respective settings if they exist):
[...]
smtpd_helo_required = yes
disable_vrfy_command = yes
strict_rfc821_envelopes = yes
invalid_hostname_reject_code = 554
multi_recipient_bounce_reject_code = 554
non_fqdn_reject_code = 554
relay_domains_reject_code = 554
unknown_address_reject_code = 554
unknown_client_reject_code = 554
unknown_hostname_reject_code = 554
unknown_local_recipient_reject_code = 554
unknown_relay_recipient_reject_code = 554
unknown_sender_reject_code = 554
unknown_virtual_alias_reject_code = 554
unknown_virtual_mailbox_reject_code = 554
unverified_recipient_reject_code = 554
unverified_sender_reject_code = 554
smtpd_recipient_restrictions =
reject_invalid_hostname,
reject_unknown_recipient_domain,
reject_unauth_pipelining,
permit_mynetworks,
permit_sasl_authenticated,
reject_unauth_destination,
reject_rbl_client multi.uribl.com,
reject_rbl_client dsn.rfc-ignorant.org,
reject_rbl_client dul.dnsbl.sorbs.net,
reject_rbl_client list.dsbl.org,
reject_rbl_client sbl-xbl.spamhaus.org,
reject_rbl_client bl.spamcop.net,
reject_rbl_client dnsbl.sorbs.net,
reject_rbl_client cbl.abuseat.org,
reject_rbl_client ix.dnsbl.manitu.net,
reject_rbl_client combined.rbl.msrbl.net,
reject_rbl_client rabl.nuclearelephant.com,
permit
[...]
Restart Postfix afterwards:
/etc/init.d/postfix restart