What does it mean "Suspicious process running under user mailnull"

I receive this alert from my WHM panel.
What does it mean? Do I have to do anything?

lfd on fff: Suspicious process running under user mailnull

Time:    Tue Feb 24 10:51:17 2015 +0200
PID:     29327 (Parent PID:29324)
Account: mailnull
Uptime:  74 seconds


Executable:

/home/virtfs/fff/usr/sbin/exim


Command Line (often faked in exploits):

/usr/sbin/exim -Mc 1YQBBq-000004-Pv


Network connections by the process (if any):

tcp: 89.19.23.155:53717 -> 89.19.23.155:110
tcp: 89.19.23.154:55920 -> 91.102.160.103:25


Files open by the process (if any):

/home/virtfs/fff/dev/null
/home/virtfs/fff/dev/null
/home/virtfs/fff/dev/null
/home/virtfs/fff/var/spool/exim/input/q/1YQBBq-000004-Pv-D
/home/virtfs/fff/tmp/tmpfqsXsdu (deleted)
/home/virtfs/fff/var/log/exim_mainlog
/home/virtfs/fff/var/spool/exim/msglog/q/1YQBBq-000004-Pv
/home/virtfs/fff/var/spool/exim/input/q/1YQBBq-000004-Pv-J
/home/virtfs/fff/etc/mailips
/home/virtfs/fff/etc/mailhelo
LVL 1
myyisAsked:
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KimputerConnect With a Mentor Commented:
I suspect this happened after a reboot?
While I don't know the exact reason, it's just one of those pre-programmed warning systems, of which the rules you may or may not figure out in time. There rules aren't like magic, and are probably fixed. See it as a false-positive that can happen once in a while, where your normal operation clashes with the warning system.
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KimputerCommented:
Your server is sending and/or receiving mail (pop/smtp). Are you aware of this? Did you have some email functions enabled? Some website forms/scripts?
If NOT, you have to find out why you are sending/receiving emails. If yes, check those IP numbers (if they are where you want to connect to), or check other email logs if those are from "correct" email, or from spam/malware.
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myyisAuthor Commented:
Yes the server sends emails
1. When users are assigned to some tasks
2. Password reset emails
etc.

But I have received this warning only once. Everyday dozens of emails are sent. May be an email my server sent was treated like a spam. Is that the case?
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KimputerCommented:
As long as you know this IP: 91.102.160.103 as being from a server from someone you needed to contact, you don't need to worry.
If you still don't trust it, find the message file 1YQBBq-000004 and read what's inside (if file still available). If not available try to get the recipients email address from the logs to see if it's someone you know.
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myyisAuthor Commented:
At whm  I found the details of the mail. Everything seems ok. So why I received that email?

Event:      success
Sender User:      fff
Sender Domain:      tr1.fff.com
Sender:      ff@tr8.fff.com
Sent Time:      Feb 24, 2015 10:50:10 AM
Sender Host:      localhost
Sender IP:      127.0.0.1
Authentication:      localuser
Spam Score:      0
Recipient:      nurvet@hhh.com.tr
Delivered To:      nurvet@hhh.com.tr
deliveryuser:      -remote-
deliverydomain:      
Router:      lookuphost
Transport:      remote_smtp
Out Time:      Feb 24, 2015 10:51:10 AM
ID:      1YQBBq-000004-Pv
Delivery Host:      mail.hhh.com.tr
Delivery IP:      91.102.160.103
Size:      15.84 KB
Result:      Message accepted
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gheistCommented:
It means you have been hacked.
Exim does in no case connect to 110/tcp aka POP3.
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myyisAuthor Commented:
Hi gheist,
What do you suggest me to do. How can clean it up, any comment?
Thank you.
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gheistCommented:
Capture spool file of
1YQBBq-000004-Pv
It has the exploit.
and upgrade exim and glibc.
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myyisAuthor Commented:
I have checked it again and saw nothing weird at the php file.
 I got the warning only once but the mail (1YQBBq-000004-Pv)  and dozens of similar mails are sent automatically  to the same recipient and recipients . Everything seems normal.

This is the function that sends the emails. Is there anything strange with that?

function SendEmail($to, $from, $body, $subject)
{
      $headers = "From: " . $from . "\n";
      $headers .= 'MIME-Version: 1.0' . "\n";
      $headers .= 'Content-type: text/html; charset=iso-8859-1' . "\n";
      mail ($to, $subject, $body, $headers);
}
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gheistCommented:
Do you sanitize parameters?
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myyisAuthor Commented:
Yeah that may be the  point, the body is inserted by the user. Do you suggest anything to sanitize?
And what you say about the Exim and 110/tcp? Do you see anything weird?
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gheistConnect With a Mentor Commented:
You need to trace  one PHP mail() call on exim
Or just break blind command posting by adding 1s delay to each SMTP response.
I think it posts by /usr/lib/sendmail, so make sure you escape each field to the level sendmail command can clean up later.
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Mbekezeli MhlangaInternet Addict Commented:
I'm surprised at all these comments and yet this is the "experts exchange"

That is just a CSF Firewall warning to say that it has detected a file that is not registered by default on the operating system , mailnull which happens to be a spam control engine .

All you have to do to fix these emails from coming in is to add exim to the ignore list


On the ConfigServer Security & Firewall plugins page,
scroll down until you see"lfd - Login Failure Daemon" section,
just below "lfd restart" button,
there is a dropdown menu
select "csf.pignore, Process Tracking" & click edit,
at the end of the file add exim to the ignore list

exe:/home/virtfs/fff/usr/sbin/exim

That should solve the problem
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gheistCommented:
Explain what EXIM has to do with port 110...
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Mbekezeli MhlangaInternet Addict Commented:
Port 110 is for pop3 , do i need to explain what exim has to do with pop3 ?
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gheistCommented:
Yes, exim does not implement pop3 server or pop3 client.
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