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linux - Has this server been compromised?

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A friend is running a VPS
(CentOS)




His business partner was the
sysadmin but has left him high and dry to look after the system. So, I've been asked to
help out in fixing an apparent spam problem. His IP address got blacklisted for
unsolicited mail. I'm not sure where to look for a problem, but I started with netstat
to see what open connections were running. It looks to me like he has remote hosts
connected to his SMTP server. Here's the
output:



 Active Internet
            connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address
            State 
tcp 0 0 78.153.208.195:imap 86-40-60-183-dynamic.:10029 ESTABLISHED
            
tcp 0 0 78.153.208.195:imap 86-40-60-183-dynamic.:10010 ESTABLISHED
            
tcp 0 1 78.153.208.195:35563 news.avanport.pt:smtp SYN_SENT 
tcp 0
            0 78.153.208.195:35559 vip-us-br-mx.terra.com:smtp TIME_WAIT 
tcp 0 0
            78.153.208.195:35560 vip-us-br-mx.terra.com:smtp TIME_WAIT 
tcp 1 1
            78.153.208.195:imaps 86-40-60-183-dynamic.:11647 CLOSING 

tcp 1 1
            78.153.208.195:imaps 86-40-60-183-dynamic.:11645 CLOSING 
tcp 0 0
            78.153.208.195:35562 mx.a.locaweb.com.br:smtp TIME_WAIT 
tcp 0 0
            78.153.208.195:35561 mx.a.locaweb.com.br:smtp TIME_WAIT 
tcp 0 0
            78.153.208.195:imap 86-41-8-64-dynamic.b-:49446 ESTABLISHED


Does this indicate
that his server may be acting as an open relay? Mail should only be outgoing from
localhost.



Apologies for my lack of knowledge
but I don't work on linux in my day
job.




/>

EDIT:
Here's
some output from /var/log/maillog which looks like it may be
the result of spam. If it appears to be the case to others, where should I look next to
investigate a root cause? I put the server IP through www.checkor.com and it came back
clean.



Jun 29 00:02:13
            vps-1001108-595 qmail: 1309302133.721674 status: local 0/10 remote 9/20
Jun 29
            00:02:13 vps-1001108-595 qmail: 1309302133.886182 delivery 74116: deferral:
            200.147.36.15_does_not_like_recipient./Remote_host_said:_450_4.7.1_Client_host_rejected:_cannot_find_your_hostname,_[78.153.208.195]/Giving_up_on_200.147.36.15./
Jun
            29 00:02:13 vps-1001108-595 qmail: 1309302133.886255 status: local 0/10 remote
            8/20
Jun 29 00:02:13 vps-1001108-595 qmail: 1309302133.898266 delivery 74115:
            deferral:
            187.31.0.11_does_not_like_recipient./Remote_host_said:_450_4.7.1_Client_host_rejected:_cannot_find_your_hostname,_[78.153.208.195]/Giving_up_on_187.31.0.11./
Jun
            29 00:02:13 vps-1001108-595 qmail: 1309302133.898327 status: local 0/10 remote
            7/20
Jun 29 00:02:14 vps-1001108-595 qmail: 1309302134.137833 delivery 74111:
            deferral:
            Sorry,_I_wasn't_able_to_establish_an_SMTP_connection._(#4.4.1)/

Jun
            29 00:02:14 vps-1001108-595 qmail: 1309302134.137914 status: local 0/10 remote
            6/20
Jun 29 00:02:19 vps-1001108-595 qmail: 1309302139.903536 delivery 74000:
            failure:
            209.85.143.27_failed_after_I_sent_the_message./Remote_host_said:_550-5.7.1_[78.153.208.195_______1]_Our_system_has_detected_an_unusual_rate_of/550-5.7.1_unsolicited_mail_originating_from_your_IP_address._To_protect_our/550-5.7.1_users_from_spam,_mail_sent_from_your_IP_address_has_been_blocked./550-5.7.1_Please_visit_http://www.google.com/mail/help/bulk_mail.html_to_review/550_5.7.1_our_Bulk_Email_Senders_Guidelines._e25si1385223wes.137/
Jun
            29 00:02:19 vps-1001108-595 qmail: 1309302139.903606 status: local 0/10 remote
            5/20
Jun 29 00:02:19 vps-1001108-595 qmail-queue-handlers[15501]: Handlers
            Filter before-queue for qmail started
            ...


EDIT
#2
Here's the output of netstat -p
with the imap and imaps lines removed.
I also removed my own ssh
session



Active Internet
            connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address
            State PID/Program name 

tcp 0 1 78.153.208.195:40076
            any-in-2015.1e100.net:smtp SYN_SENT 24096/qmail-remote. 
tcp 0 1
            78.153.208.195:40077 any-in-2015.1e100.net:smtp SYN_SENT 24097/qmail-remote.
            
udp 0 0 78.153.208.195:48515 125.64.11.158:4225 ESTABLISHED
            20435/httpd


EDIT />As it turns out, the server had been hacked due to a vulnerability in OSCommerce
and a number of PHP scripts were being run by remote clients to send mail. This was due
to the security settings of 777 on the
/var/www/vhosts//httpdocs/images
directory



Answer





This,



tcp 0 0
            78.153.208.195:imap
            86-40-60-183-dynamic.:10029



is
an external connection using IMAP to read mail from a mailbox on your
server.



This,



tcp
            0 1 78.153.208.195:35563 news.avanport.pt:smtp
            SYN_SENT


is your
server sending outbound SMTP mail to
news.avanport.pt




Without knowing more
about what it is and is not supposed to be doing, neither of those things are initially
suspicious.



You will need to use mailqueue,
check out /var/log/mail* and the mail config to work out if it's right or not, or
provide more info in the question.


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