Estou executando o Ubuntu 14.04 e tenho um servidor de e-mail e um site hospedados.
Ultimamente tenho recebido dezenas de milhares de "retorno ao remetente e mensagens de erro de e-mail "atrasadas" para o spam do Viagra e tais supostamente originadas do meu servidor.
Verificou o provável malware do Linux, nada foi encontrado. Maldetect instalado - não encontrou nada também.
O que posso fazer para descobrir se tenho um spambot no meu sistema?
Aqui está meu main.cf:
# See /usr/share/postfix/main.cf.dist for a commented, more complete version
# Debian specific: Specifying a file name will cause the first
# line of that file to be used as the name. The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname
smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu) biff = no
# appending .domain is the MUA's job. append_dot_mydomain = no
# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h
readme_directory = no
# TLS parameters smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key smtpd_use_tls=yes smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.
myhostname = mail.xxxxxxx.org
# alias_maps = hash:/etc/aliases
# alias_database = hash:/etc/aliases myorigin = xxxxxxx.org mydestination = relayhost = mynetworks = 127.0.0.1, 192.168.0.0/24
# [::ffff:127.0.0.0]/104 [::1]/128 192.168.0.0/24
# mynetworks_style = host mailbox_size_limit = 0 recipient_delimiter = + inet_interfaces = all masquerade_domains = mail.xxxxxxx.org local_recipient_maps =
# how long if undelivered before sending warning update to sender delay_warning_time = 4h
# how long to keep message on queue before return as failed.
# some have 3 days, I have 16 days as I am backup server for some people
# whom go on holiday with their server switched off. maximal_queue_lifetime = 7d
# max and min time in seconds between retries if connection failed minimal_backoff_time = 1000s maximal_backoff_time = 8000s
# how long to wait when servers connect before receiving rest of data smtp_helo_timeout = 60s
# how many address can be used in one message.
# effective stopper to mass spammers, accidental copy in whole address list
# but may restrict intentional mail shots. smtpd_recipient_limit = 16
# how many error before back off. smtpd_soft_error_limit = 3
# how many max errors before blocking it. smtpd_hard_error_limit = 12
# Requirements for the HELO statement smtpd_helo_restrictions = permit_mynetworks, warn_if_reject reject_non_fqdn_hostname, reject_invalid_hostname, permit
# Requirements for the sender details smtpd_sender_restrictions = permit_mynetworks, warn_if_reject reject_non_fqdn_sender, reject_unknown_sender_domain, reject_unauth_pipelining, permit_sasl_authenticated, permit
# Requirements for the connecting server smtpd_client_restrictions = reject_rbl_client sbl.spamhaus.org, reject_rbl_client blackholes.easynet.nl, reject_rbl_client dnsbl.njabl.org
# Requirement for the recipient address
smtpd_recipient_restrictions = reject_invalid_hostname,
reject_unknown_recipient_domain, reject_unauth_pipelining, reject_non_fqdn_recipient,
permit_mynetworks,
permit_sasl_authenticated,
reject_unauth_destination, check_policy_service unix:private/policy,
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, check_policy_service inet:127.0.0.1:10023,
permit
# require proper helo at connections smtpd_helo_required = yes
# waste spammers time before rejecting them smtpd_delay_reject = 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
# not sure of the difference of the next two
# but they are needed for local aliasing alias_maps = hash:/etc/postfix/aliases alias_database = hash:/etc/postfix/aliases
# this specifies where the virtual mailbox folders will be located virtual_mailbox_base = /var/spool/mail/virtual
# this is for the mailbox location for each user virtual_mailbox_maps = mysql:/etc/postfix/mysql_mailbox.cf
# and this is for aliases virtual_alias_maps = mysql:/etc/postfix/mysql_alias.cf
# and this is for domain lookups virtual_mailbox_domains = mysql:/etc/postfix/mysql_domains.cf
# this is how to connect to the domains (all virtual, but the option is there)
# not used yet
# transport_maps = mysql:/etc/postfix/mysql_transport.cf
virtual_uid_maps = static:5000 virtual_gid_maps = static:5000
content_filter = amavis:[127.0.0.1]:10024
# SASL smtpd_sasl_auth_enable = yes
# If your potential clients use Outlook Express or other older clients
# this needs to be set to yes broken_sasl_auth_clients = no smtpd_sasl_security_options = noanonymous smtpd_sasl_local_domain =
Não é necessário que seu sistema esteja comprometido; provavelmente você só tem uma retransmissão de email aberta , que os spammers podem explorar para enviar spam. Basicamente, eles estão explorando seu servidor SMTP para enviar seus e-mails de spam.
Assegure-se de que seu servidor de e-mail aceite apenas mensagens de localhost ou ative a autenticação SMTP para clientes remotos. (Como fazer isso depende do software do servidor de correio que você está executando.)