nixCraft Linux Sys Admin Blog

Linux vs Mac OS X vs Vista - Who will get Hacked / Cracked First?

Posted: 27 Mar 2008 01:18 PM CDT

The most anticipated matchup in the cracker (or hacker) world is going on to take control of a computer using zero day vulnerability. Checkout official site for more information about the Pwn2Own contest. The prize is US $20,000, plus you get to keep the laptop.

Postfix and MS-Exchange Mail Server Affected by ORDB.org Spam Service

Posted: 27 Mar 2008 01:03 PM CDT

Since y’day I noticed one of our article related to ORDB.org spam blocker receiving lots of traffic. I received couple of calls from our clients because most emails was getting bounced via Exchange or Postfix mail server.

ORDB is now configured to return each IP as spam source

ORDB was a database of open relay email servers, provided until 2006 as a voluntary service to block spam. Now ORDB.org service has been re-activated and it is returning every IP address queried as being on its blacklist. I guess this was done to punish lazy sys admin / mail administrators

If you or your mail server / gateway / firewall querying relays.ordb.org; please stop it immediately. If you query relays.ordb.org - mail server will rejecting all incoming mails from that server.

Symantec Mail Security for MS-Exchange Server - Spam Filter

Symantec Mail Security for Microsoft Exchange configuration in the list of Anti-spam blacklist servers including relays.ordb.org. Immediately remove the entry.

Remove ORDB.ORG from MS-Exchange Server Spam Filter

In Exchange Server 2003 you can find the feature for blacklist support within the global settings of your organization. Visit MS-Exchange System Manager > Global Settings > Message Delivery Properties -> Connection Filtering tab > Remove relays.ordb.org

Remove Linux / UNIX - Postfix Mail Server - Spam Filter

Open postfix configuration file and remove the following line:
reject_rbl_client relays.ordb.org,
Restart postfix mail server:
# service postfix restart

History and Culture of Unix Programming - The Art of Unix Programming

Posted: 27 Mar 2008 03:35 AM CDT

The Art of Unix Programming by Eric Raymond is a book about the history and culture of Unix programming from its earliest days in 1969 to now, covering both genetic derivations such as BSD and conceptual ones such as Linux.

You should read this book if you are an experienced Unix programmer who is often in the position of either educating novice programmers or debating partisans of other operating systems, and you find it hard to articulate the benefits of the Unix approach.

You should read this book if you are a C, C++, or Java programmer with experience on other operating systems and you are about to start a Unix-based project.

You should read this book if you are a Unix user with novice-level up to middle-level skills in the operating system, but little development experience, and want to learn how to design software effectively under Unix.

You can read HTML version of “The Art of Unix Programming” online at Eric’s website.

Download of the day: Wackamolem ~ Making a Cluster Highly Available

Posted: 27 Mar 2008 03:23 AM CDT

Wackamole is an interesting application that helps with making a cluster highly available. It runs a service using multiple DNS RR records without the worry of one of the machines crashing — if the machine crashes, the virtual IP addresses it was responsible for will be managed by the remaining machines in the cluster. Wackamole is quite unique in that it operates in a completely peer-to-peer mode within the cluster. From the project home page:

Wackamole is an application that helps with making a cluster highly available. It manages a bunch of virtual IPs, that should be available to the outside world at all times. Wackamole ensures that a single machine within a cluster is listening on each virtual IP address that Wackamole manages. If it discovers that particular machines within the cluster are not alive, it will almost immediately ensure that other machines acquire these public IPs. At no time will more than one machine listen on any virtual IP. Wackamole also works toward achieving a balanced distribution of number IPs on the machine within the cluster it manages.

Download wackamole software

Visit the wackamole project:

=> wackamole web site

What Would Cause a Lot of ARP Broadcasts From One System / Machine

Posted: 27 Mar 2008 03:06 AM CDT

Q. I’m experiencing decreased network performance due to ARP broadcasts coming from one system. What would cause a lot of ARP broadcasts from one server / computer?

Answer to "What Would Cause a Lot of ARP Broadcasts From One System / Machine"