Everything Has Changed
See how Intel developed the cure for deskside help visits in this video directed by Christopher Guest of Spinal Tap fame.
Click here.
Win a Laptop in the Intel Resource Center Scavenger Hunt
Scour the Internet.com Intel Resource Center for clues that spell out the name of an Intel technology. Collect the letters and, with the help of one final clue, arrange the letters to get the name of the Intel technology and you can be entered to win a Lenovo x300 laptop or an Apple iPod Touch.
Start your hunt here! »
Workstations Products Platforms Brief
Intel’s family of workstation platforms gives you the tools to move from serial to parallel workflows and enables you to iterate through alternatives faster and innovate more.
Click here.
June 20, 2006 Tip of the Trade: Sendmail's Greet_Pause By Carla Schroder
Slamming is a popular spammer tactic in which the spammer quickly fires off SMTP messages without waiting for responses from the receiving server. A poorly behaved MTA will then accept traffic from the spammer, instead of rejecting it as it should. But even well-behaved MTAs are affected because of the sheer volume of traffic with which they are forced to deal. The venerable sendmail, as of version 8.13, has a nifty feature called "greet_pause" that not only rejects incorrect SMTP transactions, but also discourages re-sends.
In a normal SMTP transaction, the client first connects and the server is supposed to send back a "220" greeting, something like:
$ telnet mail.foo.org 25
Trying 12.34.56.78...
Connected to foo.com.
Escape character is '^]'.
220-host6.foo.org ESMTP Sendmail 8.13.6/8.13.6; Wed, 14 Jun 2006 18:04:49 -0600
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.
Then, the client says "ehlo" or "helo," and the transaction continues. When the client is an impatient spammer and sends more commands without listening, the greet_pause feature detects this, marks the connection bad, and responds to anything else that tries to come over that connection with a 554 (transaction failed) message. It works by pausing briefly before sending out its 220 messages.
The pause interval is configurable, so you can tune it as needed.
Interestingly, you'll probably find that your total spam attempts drop significantly after implementing greet_pause, possibly because the spammer's software thinks it's hitting a bad server or bad addresses, or otherwise getting stuck somehow. It's an ingenious and simple method with a low-overhead that discourages significant amounts of spam.
As always, be sure to whitelist all of your important addresses. Visit sendmail.org/doc/ to learn more.
Tools:
Add serverwatch.com to your favorites Add serverwatch.com to your browser search box IE 7 | Firefox 2.0 | Firefox 1.5.x