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Wed, Dec 13, 2006 11:06 pm

Adding an Email Address to Outlook's Safe Senders List

Outlook 2003 provides the capability to add an email address to a "safe senders" list. Outlook will not apply its junk e-mail filter to email from senders on the safe senders list. However, you may have Outlook rules that will still route email from addresses on the list to the junk e-mail folder.

[ More Info ]

[/os/windows/office/outlook] permanent link

Wed, Dec 13, 2006 6:26 pm

Using pktstat to Monitor Network Traffic

Pktstat is free software for Linux and Unix systems that will display a real-time list of active connections seen on a network interface, and how much bandwidth is being used by various network connections. It partially decodes the HTTP and FTP protocols to show what filename is being transferred. X11 application names are also shown. Entries hang around on the screen for a few seconds so you can see what just happened. It also accepts filter expressions à la tcpdump.

An RPM file that can be used to install the software on Linux systems is available from http://www.stearns.org/pktstat/. As of December 13, 2006, the current version is 1.7.2q. I installed the software from the RPM file.

# wget http://www.stearns.org/pktstat/pktstat-1.7.2q-0.i386.rpm

# rpm -qip pktstat-1.7.2q-0.i386.rpm
warning: pktstat-1.7.2q-0.i386.rpm: V3 RSA/MD5 signature: NOKEY, key ID f322929d
Name        : pktstat                      Relocations: (not relocateable)
Version     : 1.7.2q                            Vendor: David Leonard
Release     : 0                             Build Date: Thu 10 Jul 2003 12:38:40 AM EDT
Install Date: (not installed)               Build Host: sparrow
Group       : Applications/Internet         Source RPM: pktstat-1.7.2q-0.src.rpmSize        : 145837                           License: Public Domain
Signature   : RSA/MD5, Thu 10 Jul 2003 12:38:40 AM EDT, Key ID 012334cbf322929d
Packager    : William Stearns <wstearns@pobox.com>
URL         : http://www.itee.uq.edu.au/~leonard/personal/software/#pktstat
Summary     : Displays a live list of active connections and what files are being transferred.
Description :
Display a real-time list of active connections seen on a network
interface, and how much bandwidth is being used by what. Partially
decodes HTTP and FTP protocols to show what filename is being
transferred. X11 application names are also shown. Entries hang around
on the screen for a few seconds so you can see what just happened. Also
accepts filter expressions a la tcpdump.

# rpm --install pktstat-1.7.2q-0.i386.rpm
warning: pktstat-1.7.2q-0.i386.rpm: V3 RSA/MD5 signature: NOKEY, key ID f322929d

Once installed the software can be run with the pktstat command. If you need to install from the source code rather from the RPM package, the steps to install the software are fairly straightforward and can be found at Bandwidth Monitoring Tools, which also lists a number of other free bandwidth monitoring tools.

The software can show you what files people are accessing on your web server in realtime as shown below:

interface: eth0
load averages: 6.3k 3.2k 1.4k bps

   bps    % desc
 779.9   2% icmp unreach port frostdragon -> ns2
            tcp adsl-68-126-206-36:2039 <-> frostdragon:http
            - GET /notebook/encyclopedia/s/slr_chibimoon.htm
            tcp adsl-68-126-206-36:2041 <-> frostdragon:http
            - 304 GET /notebook/encyclopedia/s/slr_chibimoon.htm
            tcp adsl-68-126-206-36:2042 <-> frostdragon:http
            - 304 GET /graphics/notepad.gif
            tcp adsl-68-126-206-36:2043 <-> frostdragon:http
            - 304 GET /notebook/encyclopedia/s/slr_chibimoon-title.jpg
            tcp adsl-68-126-206-36:2044 <-> frostdragon:http
            - 304 GET /notebook/encyclopedia/s/slr_chibimoon-002.jpg
            tcp adsl-68-126-206-36:2045 <-> frostdragon:http
            - 304 GET /notebook/encyclopedia/s/slr_chibimoon-001.jpg
            tcp adsl-68-126-206-36:2046 <-> frostdragon:http
            - 304 GET /notebook/encyclopedia/s/slr_chibimoon-lunapball.gif
 278.1   0% tcp adsl-68-126-206-36:2047 <-> frostdragon:http
            - 304 GET /notebook/encyclopedia/s/slr_chibimoon-ckey2.gif
  1.6k   5% tcp adsl-68-126-206-36:2048 <-> frostdragon:http
            - 304 GET /notebook/encyclopedia/s/slr_chibimoon-compact.gif

You can use tcpdump style filter expressions to limit the displayed information to just traffic you are interested in at the moment. For instance, if I just want to monitor email traffic, i.e. SMTP traffic on port 25, I can use the command pktstat port 25 when I start the program.

interface: eth0
load averages: 5.6k 1.2k 421.1 bps
filter: port 25
   bps    % desc
            tcp 245:29801 <-> frostdragon:smtp
            tcp bny92-4-82-228-126-176:1672 <-> frostdragon:smtp
 19.0k  51% tcp frostdragon:53388 <-> mx01:smtp
  55.6   0% tcp frostdragon:smtp <-> mail:22421
 18.0k  48% tcp frostdragon:smtp <-> pool-71-245-166-13:62216

By default, pktstat does not show the Fully Qualified Domain Name (FQDN) of systems. But you can change that behavior with the -F option.

         -F    Show full hostnames.  Normally, hostnames are truncated to
               the first component of their domain name before display.

For instance I could have it show the full name for systems that are exchanging email with my server with pktstat -F port 25

interface: eth0
load averages: 98.9 21.9 7.4 bps
filter: port 25
   bps    % desc
            tcp frostdragon.com:smtp <-> gateway.blackspider.com:43181

If you would prefer to see IP addresses and port numbers rather than names, you can use the -n option. E.g. I could use pktstat -n port 25 to again monitor only SMTP traffic, but this time display IP addresses rather than the host names and the port number, 25, rather than its description, which is smtp.

          -n    Do not try and resolve hostnames or service port numbers.
interface: eth0
load averages: 55.2 11.4 3.8 bps
filter: port 25
   bps    % desc
 587.1  85% tcp 66.104.202.96:36199 <-> 66.22.186.53:25
  98.4  14% tcp 66.22.186.53:25 <-> 67.172.4.27:4681

References:

  1. Bandwidth Monitoring Tools
    Planet Malaysia Blog
  2. pktstat
    By David Leonard
  3. pktstat file listing
    By William Stearns
    Mary 13, 2006

[/os/unix/linux/network] permanent link

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