Dennis Leeuw
Versie 0.2.0
The MUA is the program that a user uses to read his or her mail. Some examples: pine, mutt or Netscape (on Windows Outlook). The MUA can use several protocols to fetch the mail. The most used services are POP3, IMAP, but SMTP is also possible.
All incoming mail for a user is stored in one file in /var/spool/mail/<username>. You could read your mail with more or less, but that is not very comfortable. The most secure way of using pop3 is by using pop3 over SSL. This way you get a SSH like pop3 system.
The configuration can be found in /etc/courier/.
[META] needs more docu about interfaces to run on and protocols/ports to use.
The MTA is a program that sends mail from one server to another. This is done through the SMTP protocol. On Debian the default MTA is Exim, however there are several GNU/Linux servers that contain this functionality like: sendmail, postfix and qmail.
I like postfix so let's start with that one.
The postfix configuration files can be found in /etc/postfix/.
The most important file is main.cf. Elements in this file that need special attention:
mydestination = $myhostname, localhost.$mydomain, $mydomain
mynetworks = 192.168.1.0/24, 127.0.0.0/8
relay_domains = $mydomain
home_mailbox = Maildir/
Test the configuration with telnet:
telnet smtp.domein.nl 25 # from a Internet machine
telnet 192.168.1.1 25 # from an internal machine
mail from: user@domein.org
rcpt to: user@domein.nl
data
.
quit
The MDA is a program that incoming mail from the MTA accepts and it stores in the users mailbox, Local Delivery. The program is on almost any GNU/Linux systeem procmail. We use the functionality within postfix.
It might be that you have some pop3 mail accounts on other servers or providers. To get that mail on your local system you could use fetchmail.
A sample configuration file:
user "jsmith", with password secret1, is "johans" here;
Get the source from http://www.konarski.edu.pl/~zolw. Read the documentation, which is very good, or do:
useradd -g clamav -s /bin/false -c ``Clam Antivirus'' clamav
make
make install
The biggest challenge for an open source virus scanner is the virus signature database. The Clamav writer has written een great tool called sigtool. It is able to create a signature from a virus file with the help of another anti-virus program that detects the virus.
If you find a virus that is not detected by clamscan, but is detected by another virus scanner, do the following:
sigtool -s <string of virus-scanner that finds the virus, when it detects it> -f <file that contains the virus> -c <how the virus-scanner should be executed>
This creates a signature file. Which should be added to the clamav database. And the next time a virus passes by it will be detected by clamscan.
useradd -g vscan -s /bin/false -c ``Amavis'' vscan
Before you can use AMAVIS you first need a couple of perl modules:
libemail-valid-perl libconvert-uulib-perl \
libconvert-tnef-perl libarchive-tar-perl \
libarchive-zip-perl libcompress-zlib-perl
Then there is arc, which is not GNU/Linux ready yet. So download the source and do the following:
cd temp
tar zxvf ../arc521.tar.Z
/* long tv_sec; /* really seems to be in <sys/time.h>, */
/* long tv_usec; /* but why bother... */
/*};*/
#include <sys/time.h>
#include <time.h>
int daylight;
#else
#include <time.h>
#endif
cp arc /usr/local/bin
cp arc.1 /usr/local/man/man1/
Compile AMAVIS:
find . -exec touch 01010000 {} \;
./configure --enable-smtp --with-smtp-port=10025 --enable-postfix
make
make install
Add to /etc/postfix/main.cf:
Send an e-mail with the Eicar string to test the anti-virus functionality.
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Computer Based Learning Unit, University of Leeds.
Copyright © 1997, 1998, 1999,
Ross Moore,
Mathematics Department, Macquarie University, Sydney.
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The translation was initiated by Dennis Leeuw on 2002-05-28