ESET NOD32 ANTIVIRUS - FOR LINUX-BSD MAIL SERVER User Manual

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4.3. Content Filtering in MTA
Content ltering method is in the present a well known method used to screen and/or exclude certain dened
information from the Internet or its part. Concerning an e-mail server system the best place to implement content
ltering method is the MTA agent as an e-mail communication trac nod. The advantage of such an implementation
is that it allows one to scan e-mails inbound as well as outbound in the same implementation algorithm. On the other
hand the content ltering method is MTA dependent. The ESET comes with four content lters built for most common
MTA, i.e. MTA Sendmail, Postx, Exim and QMail. These are reviewed in the following sections.
4.3.1. Content ltering in MTA Postx
The MTA Postx content lter requirements are fullled by nod32smtp daemon. To congure nod32smtp for this
purpose the following parameters must be specied in section [smtp] of the main NOD32 conguration le.
agent_enabled = yes
listen_addr = “localhost“
listen_port=2526
server_addr = “localhost“
server_port=2525
After reread of the newly created NOD32 conguration using command:
/etc/init.d/nod32d reload
the nod32smtp module will listen on port 2526 and will forward all communication from this port to the local port
2525.
In the next step, add the following specication into the ’/etc/postx/master.cf’ conguration le.
localhost:2525inetn-n--smtpd
-ocontent_lter=
-omyhostname=nod32.yourdomain.com
Note that the ’yourdomain.com’ part of the
’myhostname’ parameter must be in your case replaced
by an appropriate server’s domain specication. Note also
that the MTA Postx does not like when the ’yourdomain.
com’ part of ’myshostname’ parameter above matches
domain name specied in the parameter ’myhostname’
of the ’/etc/postx/main.cf’ conguration le. The trick
to overcome this problem relies on using IP address in
’myhostname’ parameter of ’/etc/postx/main.cf’ while
DNS name of the domain name used in ’/etc/postx/
master.cf’.
Finally, add ’content_lter’ specication into ’/
etc/postx/main.cf’ conguration le by entering the
following command.
postconf-e“content_lter=smtp:localhost:2526“
Entire entire process described above is illustrated in gure 4-4.
TCP port 2525
POSTFIX
CLEANUP
SMTP
SMTPD LOCAL
QUEUE
PICKUP
TCP port 2526
SMTPD SMTP
NOD32SMPT
Figure 4-4. Bidirectional scanning scheme of an nod32smtp
module working as a content lter.
NOD32 for Linux/BSD Mail Server

ESET NOD32 ANTIVIRUS - FOR LINUX-BSD MAIL SERVER Specifications

General

Type	Antivirus Software
Supported Operating Systems	Linux, BSD
Email Scanning	Yes
Real-time Protection	Yes
License	Commercial
Purpose	Mail Server Protection
Antivirus Engine	ESET NOD32
Updates	Automatic updates
Management	Remote Management