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       p3scan_readme - readme for the p3scan tool


       This  is  a  fully transparent proxy-server for POP3, SMTP, and limited
       POP3S Clients. It runs on a Linux  box  with  iptables  (for  port  re-

       It  can be used to provide email scanning from/to the internet, to/from
       any internal network and is ideal for helping to  protect  your  "Other
       OS"  LAN  from  harm, especially when used synergically with a firewall
       and other Internet Proxy servers.

       It is designed to enable scanning of email messages for Viruses, Worms,
       Trojans,  Spam  (read  as  "Un-solicited  Bulk  Email"),  and  harmfull
       attachments.  Because viewing HTML  mail  can  enable  a  "Spammer"  to
       validate an email address (via web bugs), it can also provide dangerous
       HTML tag stripping.


       It works typically in situations where the linux box lies  between  the
       network you wish to protect and the "outer world".

       You  have  to  set  up  a port redirection rule with iptables (see "IP-
       Tables / Port redirecting") so that all connections  from  e.g.  inside
       your  office  to  any POP3, POP3S, and SMTP server outside in the world
       will not leave your router, but come to a local port, on  which  P3Scan

       P3Scan  receives  the original destination address of the "outer world"
       server from the Linux kernel and connects to that address.

       Anything received from the client will be sent to the server, and  vice
       versa  but  with  a little enhancement: when a message is sent from the
       server it’s parsed, stored into a file, and  scanned.  If  a  virus  is
       found  a  virus  notification  is sent instead of the original infected
       message, which can be quarantined or optionally deleted. If the message
       is  destined  for  a  server  and  a virus is found, the client will be
       notified that the server rejected their message due to a virus.

       The message can also be scanned for spam,  have  potentially  dangerous
       attachments   renamed,   and  have  potentially  malicious  HTML  parts
       stripped. In the case of incoming messages, this is  performed  in  the
       following order:

       Attachments are scanned/renamed/deleted (optional)
       The message is scanned for virus’s
       The message is scanned for SPAM (optional)
       The message is parsed for web bugs (optional)

       It   should   be   possible   to   use  any  virus  scanner  using  the
       scannertype=basic configuration option. Known to work with this scanner
       are FRISK F-Prot and Clam Anti Virus scanners.

       P3Scan  provides  other  scannertype’s  for  scanning  using Kaspersky,
       Trophie, Clam (TCP) Anti-Virus Daemon’s and also a bash script.  Any  C
       programmer can easily adapt p3scan for other scan-daemons.

       Neither  the  client  nor the server has to be configured. None of them
       will ever notice that there’s a mail scanner. From the server point  of
       view  the  incoming  connections  are  from  the linux box IP. From the
       client point of view the only evidence of the presence  of  p3scan  are
       virus notifications and some additional X-headers.


       iptables - Normally installed by default on major Linux Distributions.

       libpcre - Normally installed by default on major Linux Distributions.

       ripmime - Needed if your virus scanner does not support email.

       An Anti-Virus program
          P3Scan is known to work with:
             Kaspersky Anti-Virus for Linux (AVPD)
             Trophie Anti-Virus Daemon
             FRISK F-Prot Antivirus
             Clam Anti-Virus
             F-Secure Anti-Virus
          Any other virus scanner that can output it’s report to the console (stdout) so that it can be captured with "2>&1".
       DSPAM (optional) -
       Mail::SpamAssassin (optional) -
       renattach (optional) -
       p3pmail (optional) -

       Kernel:  The  following  kernel-parameters  have  to  be enabled to get
       P3Scan to work.  If you have no clue about kernel-compiling, then  here
       is  some  good  news: Most of Linux Distributions (with kernel 2.4.x or
       greater) support what we need by default. However, if your distribution
       does  not  have it, please read your system documentation on how to add
       it to your kernel.



       Change to the directory where you untar’ed the  program  and  make  any
       system  specific  changes  as  needed to the "user options" area of the
       Makefile, then as user: $ make and as root (su root) # make install

       The only binary will be copied to /usr/sbin/p3scan.

       Make install will also copy p3scan.conf and  the  p3scan-xx.mail  files
       into    /etc/p3scan    while    creating    directories    /etc/p3scan,
       /var/run/p3scan,  /var/spool/p3scan,  /var/spool/p3scan/children,   and
       /var/spool/p3scan/notify.   It  will  also  create  a  symbolic link of
       /etc/p3scan/p3scan.mail to the language file specified in the Makefile.

       After  this,  you  must  prepare  your  configuration file as described

       Preparing / Manual Configuration:

       If you decide not to use "make install" (for example,  you  don’t  want
       gcc  on  your  firewall  machine  where p3scan is going to run). Please
       ensure the following directories are created and that  they  are  owned
       and readable/writable by only the user "mail" (default).

       As  root, create the following directories: # mkdir /etc/p3scan # mkdir
       /var/run/p3scan  #  mkdir  -p  /var/spool/p3scan/children  #  mkdir  -p

       Make  them  "owned"  by  the  user  "mail" (default): # chown mail.mail
       /etc/p3scan # chown mail.mail  /var/run/p3scan  #  chown  -R  mail.mail

       Then  make  them read/write by only our user: # chmod 700 /etc/p3scan #
       chmod 700 /var/run/p3scan # chmod -R 700 /var/spool/p3scan

       If you don’t have the user "mail" and do not know how  to  create  this
       user,  please see your operating systems documentation on how to create
       a user.

       Change the symlink /etc/p3scan/p3scan.mail if you wish (this points  to
       the  template which is sent instead of a virus). If you use any special
       character (like German-umlauts) don’t forget  to  set  the  charset  to
       "utf8"  (charset="utf8"  vice  charset="iso-8859-1").  Also, ensure the
       leading dot at the end of the file is there and has a  carriage  return
       after the dot.


       The configuration file defaults to /etc/p3scan/p3scan.conf

       This file is a mixture of configuration data and documentation and MUST
       be modified to work  correctly  upon  initial  installation.  You  must
       specify AT LEAST how to call your anti-virus program and how to extract
       the virus name (if one is found).

       The purpose of p3scan is to provide virus  protection  to  an  internal
       network.   So,  not having a virus scanner is not an option. That being
       said, if you still do not want a virus scanner enabled,  you  can  just
       set the scannertype/scanner to basic/"/usr/bin/cat".

       Currently, the default configuration is as follows (see p3scan.conf for
       more info):

          The PID file is stored in: pidfile = /var/run/p3scan/
          The maximum simultaneous scans is: maxchilds = 10
          We listen to any address: ip =
          We listen only on: port = 8110
          targetip and targetport are disabled.
          We extract destination url:port from iptables redirected packets.
          We run as: user = mail
          We create notification mails in: notifydir = /var/spool/p3scan/notify
             before sending.
          We default to storing infected messages in: virusdir = /var/spool/p3scan
          We keep infected mail.
             "justdelete" is not set.
          We send emergency notification emails to root and postmaster @localhost.
          We notify only the email client when a virus is detected.
             "extra" is not set.
          We use the default /bin/mail to send extra notification email when required.
          We do not check remaining disk space before scanning mail.
             "bytesfree" is not set
          We DO NOT have an Anti-Virus program selected, scanner return code, nor
             regular expression on how to extract a virus name.
             "scanner" is not set
             "viruscode" is not set
             "virusregexp" is not set
          We DO NOT have any "Good" return codes set other than "0" (zero).
             "goodcode" is not set
          We DO NOT demime the message or separate attachments from the original mail
             before scanning.
             "demime" is not set
          We DO NOT send entire lines of email header while processing to keep the
             email client "alive". We send characters instead.
             "broken" is not set.
          The default timeout is 30 seconds when processing a large email message.
          We DO NOT check for email marked as "Spam" by your ISP.
             "ispspam" is not set.
          We DO NOT check for "Spam".
             "checkspam/spamcheck" is not set
          We DO NOT rename attachments.
             "renattach" is not pointing to any external program.
          We DO NOT parse HTML code.
             "overwrite" is not pointing to any external program.
          We DO NOT have debug messages being displayed.
             *"debug" is not set.
             * Note: The recommended debug procedure is to call p3scan as such:
                p3scan -d > debug 2>&1
                You can then keep track of the debug messages on another terminal
               with: tail -n 50 -f debug
          We report all program steps to syslog less debug info.
             "quiet" is not set.
          The Virus Report template defaults to /etc/p3scan/p3scan.mail which is
             a symlink to /etc/p3scan/p3scan-xx.mail generated during "make install",
             where xx equals the LANG option set in the Makefile.
          We do not copy the virus template message for the bash scanner to modify.
             "altvnmsg" is not set.
          We generate the Virus Report Subject line as:
            "[Virus] found in a mail to you:" <virus name>
            you can change this with the "subject" line in p3scan.conf.
          We generate the Virus Report file disposition line (when justdelete is set):
          notify = Per instruction, the message has been deleted.
          When an outgoing message is rejected, the default of "Virus detected! P3scan
             rejected message!" is used.
          Outgoing message size is not checked before parsing.
          The port for SSL messages is 995.
          We do not generate Virus Definition data for outgoing/notification messages.
             "footer" is not set.

       IP-Tables / Port redirecting:

          Rules like:

       iptables -t nat -A PREROUTING -p tcp -i eth0 --dport pop3 -j REDIRECT --to 8110
       iptables -t nat -A PREROUTING -p tcp -i eth0 --dport smtp -j REDIRECT --to 8110
       iptables -t nat -A PREROUTING -p tcp -i eth0 --dport pop3s -j REDIRECT --to 8110

          are enough. Change eth0 to your device for the inbound connections (your
          office or home network).

          Also, "pop3", "smtp", and/or "pop3s" must be defined in your "services" file.
          Normally locate at: /etc/services.

          If it is not defined, enter the definition you have for 110/tcp. IE: pop-3, or
          just enter the port number(s). IE: 110, 25, or 995

       Spam Checking

          The spam checking capability of p3scan has only been tested using
          DSPAM >= 3.0.0-rc2 and Mail::SpamAssassin v2.6 >= v3.0.1

          If using dspam, you need to install the program according to the
          documentation found at

          The recommended procedure is the virtual-users interface of the mysql

          If you will be scanning for spam using SpamAssassin, you need to install the
          program according to the documentation found at

          The easiest (as fastest) interface to Mail::SpamAssassin is through it’s
          daemon program "spamd" using "spamc".

          You can start spamd as follows before running p3scan:
          *Note: This example is for using SpamAssassin w/mysql
          /usr/bin/spamd -d -u spamd -x -q &

       SSL Message parsing:

          We are able to perform limited checking of messages using SSL.
          To use this feature, you must tell your email client NOT to use SSL and just
          change the pop3 port from 110 to 995. If p3scan sees a destination port of 995
          (or whatever port "sslport" is set to) it will initiate an SSL conversation.

          NOTE: This is limited support as p3scan will not show you the SSL certificate
          and will just accept any certificate as sent by the actual server.

       renattach: Is used to rename attachments and is totally configurable.

              Renattach must be compiled,  installed,  and  configured  before
              enabling  this  feature. See the renattach documentation INSTALL
              and README for further information.

       HTML Parsing: The HTML parsing option is now  an  external  program  to
       p3scan. This facilitates using any program you can find. I have written
       a separate program for this function called p3pmail which can be  found
       on the p3scan web site.

              P3PMail  will  obfuscate  the tags "href" and "src" the two most
              dangerous HTML tags (IMHO) for email. Of course, if your using a
              non-html  email  client,  you will not have to worry about "web-

       Startup: Call p3scan without any parameters,  it  will  move  into  the
       background.   You can monitor it’s operation via your systems log file.
       You should also test your installation by  sending  yourself  an  eicar
       test virus (which will not damage your system). You can get versions of
       this file at

              If you think too much information is being sent to  your  system
              logs,  you  can  enable  the  "quiet"  option. This will inhibit
              "normal" messages.

              If p3scan is started by root, it will change it’s user to "mail"
              (default) after it finishes it’s initial startup.

              If  you are using Mail::SpamAssassin, start spamd BEFORE running

       RC System / Boot up: "make install" should determine the correct p3scan
       startup file and place it in the proper directory.

              If  for  some reason this does not happen, you can add p3scan to
              your normal default startup  file.  For  example,  in  Slackware
              place p3scan as follows:

              # echo "/usr/sbin/p3scan" >> /etc/rc.d/rc.local

              and  please notify the p3scan-main mailing list of this problem.


       "p3scan" "p3scan.conf"

       BUGS/SUPPORT Please report any bugs to the p3scan support mailing  list
       accessable through:


       Jack  S. Lai <laitcg at cox dot net> and contributers (see CONTRIBUTERS