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I have some weird entries in my mail.log. What I'd like to ask is if postfix is avoiding correctly (according with the main.cf attached below) what seems to be relay attempts, presumably for spamming, or if I can enhance it's security somehow.

Feb  2 11:53:25 MYSERVER postfix/smtpd[9094]: connect from catv-80-99-46-143.catv.broadband.hu[80.99.46.143]
Feb  2 11:53:25 MYSERVER postfix/smtpd[9094]: warning: non-SMTP command from catv-80-99-46-143.catv.broadband.hu[80.99.46.143]: GET / HTTP/1.1
Feb  2 11:53:25 MYSERVER postfix/smtpd[9094]: disconnect from catv-80-99-46-143.catv.broadband.hu[80.99.46.143]
Feb  2 11:56:45 MYSERVER postfix/anvil[9097]: statistics: max connection rate 1/60s for (smtp:80.99.46.143) at Feb  2 11:53:25
Feb  2 11:56:45 MYSERVER postfix/anvil[9097]: statistics: max connection count 1 for (smtp:80.99.46.143) at Feb  2 11:53:25
Feb  2 11:56:45 MYSERVER postfix/anvil[9097]: statistics: max cache size 1 at Feb  2 11:53:25
Feb  2 12:09:19 MYSERVER postfix/smtpd[9302]: connect from vs148181.vserver.de[62.75.148.181]
Feb  2 12:09:19 MYSERVER postfix/smtpd[9302]: warning: non-SMTP command from vs148181.vserver.de[62.75.148.181]: GET / HTTP/1.1
Feb  2 12:09:19 MYSERVER postfix/smtpd[9302]: disconnect from vs148181.vserver.de[62.75.148.181]
Feb  2 12:12:39 MYSERVER postfix/anvil[9304]: statistics: max connection rate 1/60s for (smtp:62.75.148.181) at Feb  2 12:09:19
Feb  2 12:12:39 MYSERVER postfix/anvil[9304]: statistics: max connection count 1 for (smtp:62.75.148.181) at Feb  2 12:09:19
Feb  2 12:12:39 MYSERVER postfix/anvil[9304]: statistics: max cache size 1 at Feb  2 12:09:19
Feb  2 14:17:02 MYSERVER postfix/smtpd[10847]: connect from unknown[202.46.129.123]
Feb  2 14:17:02 MYSERVER postfix/smtpd[10847]: warning: non-SMTP command from unknown[202.46.129.123]: GET / HTTP/1.1
Feb  2 14:17:02 MYSERVER postfix/smtpd[10847]: disconnect from unknown[202.46.129.123]
Feb  2 14:20:22 MYSERVER postfix/anvil[10853]: statistics: max connection rate 1/60s for (smtp:202.46.129.123) at Feb  2 14:17:02
Feb  2 14:20:22 MYSERVER postfix/anvil[10853]: statistics: max connection count 1 for (smtp:202.46.129.123) at Feb  2 14:17:02
Feb  2 14:20:22 MYSERVER postfix/anvil[10853]: statistics: max cache size 1 at Feb  2 14:17:02
Feb  2 20:57:33 MYSERVER postfix/smtpd[18452]: warning: 95.110.224.230: hostname host230-224-110-95.serverdedicati.aruba.it verification failed: Name or service not known
Feb  2 20:57:33 MYSERVER postfix/smtpd[18452]: connect from unknown[95.110.224.230]
Feb  2 20:57:33 MYSERVER postfix/smtpd[18452]: lost connection after CONNECT from unknown[95.110.224.230]
Feb  2 20:57:33 MYSERVER postfix/smtpd[18452]: disconnect from unknown[95.110.224.230]
Feb  2 21:00:53 MYSERVER postfix/anvil[18455]: statistics: max connection rate 1/60s for (smtp:95.110.224.230) at Feb  2 20:57:33
Feb  2 21:00:53 MYSERVER postfix/anvil[18455]: statistics: max connection count 1 for (smtp:95.110.224.230) at Feb  2 20:57:33
Feb  2 21:00:53 MYSERVER postfix/anvil[18455]: statistics: max cache size 1 at Feb  2 20:57:33
Feb  2 21:13:44 MYSERVER pop3d: Connection, ip=[::ffff:219.94.190.222]
Feb  2 21:13:44 MYSERVER pop3d: LOGIN FAILED, user=admin, ip=[::ffff:219.94.190.222]
Feb  2 21:13:50 MYSERVER pop3d: LOGIN FAILED, user=test, ip=[::ffff:219.94.190.222]
Feb  2 21:13:56 MYSERVER pop3d: LOGIN FAILED, user=danny, ip=[::ffff:219.94.190.222]
Feb  2 21:14:01 MYSERVER pop3d: LOGIN FAILED, user=sharon, ip=[::ffff:219.94.190.222]
Feb  2 21:14:07 MYSERVER pop3d: LOGIN FAILED, user=aron, ip=[::ffff:219.94.190.222]
Feb  2 21:14:12 MYSERVER pop3d: LOGIN FAILED, user=alex, ip=[::ffff:219.94.190.222]
Feb  2 21:14:18 MYSERVER pop3d: LOGIN FAILED, user=brett, ip=[::ffff:219.94.190.222]
Feb  2 21:14:24 MYSERVER pop3d: LOGIN FAILED, user=mike, ip=[::ffff:219.94.190.222]
Feb  2 21:14:29 MYSERVER pop3d: LOGIN FAILED, user=alan, ip=[::ffff:219.94.190.222]
Feb  2 21:14:35 MYSERVER pop3d: LOGIN FAILED, user=info, ip=[::ffff:219.94.190.222]
Feb  2 21:14:41 MYSERVER pop3d: LOGIN FAILED, user=shop, ip=[::ffff:219.94.190.222]
Feb  3 06:49:29 MYSERVER postfix/smtpd[25834]: warning: 71.6.142.196: hostname db4142196.aspadmin.net verification failed: Name or service not known
Feb  3 06:49:29 MYSERVER postfix/smtpd[25834]: connect from unknown[71.6.142.196]
Feb  3 06:49:29 MYSERVER postfix/smtpd[25834]: lost connection after CONNECT from unknown[71.6.142.196]
Feb  3 06:49:29 MYSERVER postfix/smtpd[25834]: disconnect from unknown[71.6.142.196]
Feb  3 06:52:49 MYSERVER postfix/anvil[25837]: statistics: max connection rate 1/60s for (smtp:71.6.142.196) at Feb  3 06:49:29
Feb  3 06:52:49 MYSERVER postfix/anvil[25837]: statistics: max connection count 1 for (smtp:71.6.142.196) at Feb  3 06:49:29
Feb  3 06:52:49 MYSERVER postfix/anvil[25837]: statistics: max cache size 1 at Feb  3 06:49:29

I have Postfix 2.7.1-1 running on Ubuntu 10.10. This is my (modified por privacy) main.cf:

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

append_dot_mydomain = no


readme_directory = no


smtpd_tls_cert_file = /etc/ssl/certs/smtpd.crt
smtpd_tls_key_file = /etc/ssl/private/smtpd.key


myhostname = mymailserver.org
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = mymailserver.org, MYSERVER, localhost
relayhost = 
mynetworks = 127.0.0.0/8, 192.168.1.0/24
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
home_mailbox = Maildir/

smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination
mailbox_command = 
smtpd_sasl_local_domain = 
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
broken_sasl_auth_clients = yes
smtpd_tls_security_level = may
smtpd_tls_auth_only = no
smtp_tls_note_starttls_offer = yes
smtpd_tls_CAfile = /etc/ssl/certs/cacert.pem
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_session_cache_timeout = 3600s
tls_random_source = dev:/dev/urandom
smtp_tls_security_level = may
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You are worried because of ten spammers connecting? Wow :) ... lucky you. I really would like to have that problem. –  0xC0000022L Feb 13 '13 at 20:31
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1 Answer 1

up vote 4 down vote accepted

You are right on both.

They are standard spam attempts, and postfix is denying relaying to them. If these are your full logs, then you are lucky if you are only seeing that few attempts per day.

You can still harden it quite a lot, using SSL for example, but it didn't look like you need it.

You can change this to main.cf to force all the clients that want to relay mail to use TLS Authentication, smtpd_tls_auth_only = yes. This can cause problems with older clients. Clients from the LAN (as defined in mynetworks variable) will still be able to send mail using unencrypted connections.

You can force postfix to accept only TLS connections, but it is a very bad idea unless you are using it only to receive and send local mail:

  • Servers that don't support TLS won't be able to send or receive mail from you.
  • It's against the RFC, so it's no standard.

Just change smtpd_tls_security_level = encrypt. Again this is a bad idea.

share|improve this answer
    
Thaks for your answer... How could I force SSL?... About the spam attempts... well the domain -and the mail server- were configured just 5 days ago... So I guess I should expect more to come. –  luri Feb 3 '11 at 13:49
    
Thanks again for the further info.... I won't set TLS then. –  luri Feb 3 '11 at 18:31
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