Today I got many spammy emails into my mailbox, I looked in exim4 logs and I found some suspected activities.
I would like to understand the serverity of this attack, if I got spammy mail I can delete them and add some rules, however I want to be sure that I'm not a spammer.
I read many of these logs:
2016-03-09 07:53:12 1adXzZ-0007sb-Pz <= [email protected] H=([127.0.0.1]) [129.137.152.170] P=esmtpa A=plain: S=1298 [email protected]
2016-03-09 07:53:12 1adXzZ-0007sb-Pz no immediate delivery: more than 10 messages received in one connection
2016-03-09 08:16:57 1adXzZ-0007sb-Pz => kamikaze_****@hotmail.co.uk R=dnslookup T=remote_smtp H=mx3.hotmail.com [207.46.8.167] X=TLS1.2:ECDHE_RSA_AES_256_CBC_SHA384:256 CV=no DN="CN=*.hotmail.com" C="250 <[email protected]> Queued mail for delivery"
2016-03-09 08:16:57 1adXzZ-0007sb-Pz Completed
Please consider that:
- kamikaze_****@hotmail.co.uk (I add some asterisks for privacy) is not a known recipient and this is not a mailbox in my server.
- Realy should be permitted only to authenticated users, and here I did not find any authentication info.
- In the log there is a 250 and "Completed", so seems that no error was thrown. The sign of the log is "=>" that means outgoing message...
So, I'm a spammer? Is my server sending mails without authentication?
This is my configuration:
accept_8bitmime
acl_smtp_data = acl_check_data
acl_smtp_data_prdr = accept
acl_smtp_mail = acl_check_mail
acl_smtp_rcpt = acl_check_rcpt
admin_groups =
no_allow_domain_literals
no_allow_mx_to_ip
no_allow_utf8_domains
auth_advertise_hosts = *
auto_thaw = 0s
av_scanner = sophie:/var/run/sophie
bounce_return_body
bounce_return_message
bounce_return_size_limit = 100K
callout_domain_negative_expire = 3h
callout_domain_positive_expire = 1w
callout_negative_expire = 2h
callout_positive_expire = 1d
callout_random_local_part = $primary_hostname-$tod_epoch-testing
check_log_inodes = 0
check_log_space = 0
check_rfc2047_length
check_spool_inodes = 0
check_spool_space = 0
daemon_smtp_ports = smtp
daemon_startup_retries = 9
daemon_startup_sleep = 30s
delay_warning = 1d
delay_warning_condition = ${if or {{ !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }{ match{$h_precedence:}{(?i)bulk|list|junk} }{ match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }} {no}{yes}}
no_deliver_drop_privilege
deliver_queue_load_max =
delivery_date_remove
no_disable_ipv6
dkim_verify_signers = $dkim_signers
dns_check_names_pattern = (?i)^(?>(?(1)\.|())[^\W](?>[a-z0-9/_-]*[^\W])?)+(\.?)$
dns_csa_search_limit = 5
dns_csa_use_reverse
dns_dnssec_ok = -1
dns_retrans = 0s
dns_retry = 0
dns_use_edns0 = -1
no_drop_cr
dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
envelope_to_remove
exim_group = Debian-exim
exim_path = /usr/sbin/exim4
exim_user = Debian-exim
extract_addresses_remove_arguments
finduser_retries = 0
freeze_tell = postmaster
gecos_name = $1
gecos_pattern = ^([^,:]*)
no_gnutls_allow_auto_pkcs11
no_gnutls_compat_mode
header_line_maxsize = 0
header_maxsize = 1048576
headers_charset = UTF-8
helo_allow_chars = _
helo_lookup_domains = @ : @[]
host_lookup = *
host_lookup_order = bydns:byaddr
ignore_bounce_errors_after = 2d
no_ignore_fromline_local
keep_malformed = 4d
no_ldap_start_tls
ldap_version = -1
no_local_from_check
local_interfaces = <; ::0 ; 0.0.0.0
local_scan_timeout = 5m
local_sender_retain
log_file_path = /var/log/exim4/%slog
log_selector = +smtp_protocol_error +smtp_syntax_error +tls_certificate_verified +tls_peerdn
no_log_timezone
lookup_open_max = 25
max_username_length = 0
no_message_body_newlines
message_body_visible = 500
message_logs
message_size_limit = 50M
no_move_frozen_messages
no_mua_wrapper
mysql_servers = localhost/system/exim/mypassw
never_users =
no_perl_at_start
pid_file_path = /var/run/exim4/exim.pid
pipelining_advertise_hosts = *
prdr_enable
no_preserve_message_logs
primary_hostname = srv1.mydomain.com
no_print_topbitchars
process_log_path = /var/spool/exim4/exim-process.info
prod_requires_admin
qualify_domain = mydomain.com
qualify_recipient = mydomain.com
queue_list_requires_admin
no_queue_only
queue_only_load =
queue_only_load_latch
queue_only_override
no_queue_run_in_order
queue_run_max = 5
receive_timeout = 0s
received_header_text = Received: ${if def:sender_rcvhost {from $sender_rcvhost\n\t}{${if def:sender_ident {from ${quote_local_part:$sender_ident} }}${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}by $primary_hostname ${if def:received_protocol {with $received_protocol}} ${if def:tls_cipher {($tls_cipher)\n\t}}(Exim $version_number)\n\t${if def:sender_address {(envelope-from <$sender_address>)\n\t}}id $message_exim_id${if def:received_for {\n\tfor $received_for}}
received_headers_max = 30
recipients_max = 0
no_recipients_max_reject
remote_max_parallel = 2
retry_data_expire = 1w
retry_interval_max = 1d
return_path_remove
rfc1413_hosts = @[]
rfc1413_query_timeout = 0s
slow_lookup_log = 0
smtp_accept_keepalive
smtp_accept_max = 20
smtp_accept_max_nonmail = 10
smtp_accept_max_nonmail_hosts = *
smtp_accept_max_per_connection = 1000
smtp_accept_queue = 0
smtp_accept_queue_per_connection = 10
smtp_accept_reserve = 0
smtp_banner = $smtp_active_hostname ESMTP Exim $version_number Ubuntu $tod_full
smtp_check_spool_space
smtp_connect_backlog = 20
smtp_enforce_sync
smtp_etrn_serialize
smtp_load_reserve =
smtp_max_synprot_errors = 3
smtp_max_unknown_commands = 3
no_smtp_return_error_details
spamd_address = 127.0.0.1 783
no_split_spool_directory
spool_directory = /var/spool/exim4
sqlite_lock_timeout = 5
no_strict_acl_vars
no_strip_excess_angle_brackets
no_strip_trailing_dot
syslog_duplication
syslog_processname = exim
syslog_timestamp
tcp_nodelay
timeout_frozen_after = 1w
tls_advertise_hosts = *
tls_certificate = /etc/exim4/exim.crt
tls_dh_max_bits = 2236
tls_eccurve = prime256v1
tls_on_connect_ports = 465
tls_privatekey = /etc/exim4/exim.key
no_tls_remember_esmtp
tls_verify_certificates = ${if exists{/etc/ssl/certs/ca-certificates.crt}{/etc/ssl/certs/ca-certificates.crt}{/dev/null}}
trusted_groups =
trusted_users = uucp
untrusted_set_sender = *
uucp_from_pattern = ^From\s+(\S+)\s+(?:[a-zA-Z]{3},?\s+)?(?:[a-zA-Z]{3}\s+\d?\d|\d?\d\s+[a-zA-Z]{3}\s+\d\d(?:\d\d)?)\s+\d\d?:\d\d?
uucp_from_sender = $1
write_rejectlog
And this is the PLAIN authenticator:
plain:
driver = plaintext
public_name = PLAIN
server_advertise_condition = yes
server_condition = ${if eq{$3}{${lookup mysql{ SELECT password FROM users WHERE CONCAT(username,'@',domain)='${quote_mysql:$2}' AND smtp>0 }}}{yes}{no}}
server_set_id = $2
Yes, you are running an open relay and your server is actively used to send spam.
You should change your configuration to only let authenticated users relay, ASAP. Maybe this ServerFault question will help you doing so. Also there are plenty of good howtos out there.
As for the
H=([127.0.0.1]) [129.137.152.170]: 127.0.0.1 is what the sender says is it's hostname and 129.137.152.170 is the actual IP ofthe sender.Also you might want to contact the abuse contacts of the sender IP address(es) and inform them, they have malicious activity.
I solved the heavy hole changing the plain authenticator this way: