Monday, December 24, 2007


Season's Greetings

Wishing everyone Merry Christmas, Frohe Weihnachten, Joyeux Noël, Feliz Navidad, Bon Nadal, Glædelig Jul, Prettig Kerstfeest, Hyvaa joulua, Gledelig Jul, Sretan Bozic, Buone Feste Natalizie and wonderful holidays!


Wednesday, December 19, 2007


I, Blogger

So I have finally started my blog. While the blogosphere continues to grow at an amazing speed, some bloggers of the early days have already switched back to a static homepage they update every now and then, or gone completely offline.

Why now? No particular reason really. I have been playing with the idea of creating a blog and have written up a few blog posts locally without publishing them, just to see how I liked it and what I would have to say. (A few of those early secret blog posts still sit on my hard disk and will eventually show up here retroactively.)

Looking back, I first maintained plogs (for “paper logs”) some 20 years ago when Andrea and I were traveling around in Europe by train. Each of us would write down the experiences of the day, where we went, what we liked and disliked, just about anything that came to mind, in a small booklet. When we were both done with writing, we would read each other's notes, which was great fun.

The intended readership of these plogs was one person. The esteemed readership of this blog may be about the same size currently. By coincidence, Bernhard just started blogging too, so that makes us two late adopters and ensures each of us has at least one reader. Onward.

Next, there was a technology decision to be made: install blogging software or use a hosted service. Ed Costello had shared his experience with getting Movable Type working on pair Networks servers, reading through the steps and given that I wasn't planning to spend more than an hour or two in getting things running I chose to go with a hosted service, Blogger, and have been pretty pleased with it.

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Thursday, December 13, 2007


jQuery and Greasemonkey

Now that Fiddler stopped working for me I used Greasemonkey to modify pages on the fly to test some new functionality.

It took me a while to figure out why a global variable which one of the dynamically added scripts created was not visible to my Greasemonkey script. Of course the answer was right there in the Greasemonkey documentation: "As of Greasemonkey 0.6.4, however, user scripts now have their own JavaScript context and execute completely separately from the content document." Fortunately, the document window is also accessible as unsafeWindow, and sure enough that worked.

PS. Michael Baierl pointed out a sample Greasemonkey script to load jQuery before executing functions that depend on jQuery—nice!

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Sunday, December 9, 2007


Taking Sunday off

Andrea and I took Sunday off this week. Elias stayed with his grandparents at my sister-in-law's place, the first time ever without one of us around at night, and it worked out nicely.

We missed him on the way home already, but waking up at 10:30 a.m. without the usual "Mama, Papa, Frühstück, aussa, rasch" was very enjoyable for a change. The weather wasn't great so we stayed home and spent the day messing around.

Elias had a good time and didn't seem to miss us too much.


Friday, December 7, 2007


The 4-Hour Workweek

An interview "The Business of Life" first triggered my interest in The 4-Hour Workweek: Escape 9-5, Live Anywhere, and Join the New Rich by Timothy Ferris.

Of course even the author will readily admit that one should "not to take the four hours too literally" and it certainly makes a catchier title than "Save an hour per week for things you like", but then anything that means getting more done with less effort and having more time left for the things you really enjoy is good, right?

Ferris may get some basic facts wrong, as readers noted on, but he certainly gets his marketing right. His book must have been featured in about every TV show and newspaper by now, judging from the number of comments and the news coverage since. Some claim this book changed their lives while others feel tricked by the simple, well-known recipes -- not everyone is going to make a living from selling nutritional supplements.

Despite the criticism I ordered my copy last month (so I guess the concept worked!) and also added Getting Things Done: The Art of Stress-Free Productivity, which received favorable comments that I can relate to.

The books were in the mail today, and I will start reading them over the holidays. They probably won't significantly change my life but they should make light reading over the holidays and nicely complement the fiction books, and they may even give me some useful ideas for New Year's resolutions.

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Saturday, December 1, 2007


Spam filtering with considered harmful

DNS blacklists (DNSBL) provide information about characteristics and past observations of IP addresses and have been used in filtering spam for more than a decade. In short, a spam filter may check one or more DNSBL services to determine if the network address from where an e-mail is delivered is trustworthy or suspicious.

Besides listing addresses of known spam sources or virus-infected machines, there are lists for criteria such as network type (dial-up/cable/DSL) and configuration issues (open relays, RFC non-compliance).

One of my colleagues recently had e-mail to a client rejected by their mail gateway with the error message "554 Your Host 32.nn.nn.nn was found in the DNS BlackList at"

When he asked for help with this, my first thought was that one of our addresses had, rightly or wrongly, been listed as a spam source. However, after looking around it became clear that the recipient was blocking all mail that appeared to come from certain countries according to the database despite the disclaimer on that Website that " is NOT a list of spammers, it is an IP-to-country DNS mapping service."

What's worse in this case is that the mapping was incorrect: The whole 32/8 netblock is declared to be based in the UK: " : IP is in uk, rejected based on geographical location". There may be some UK based addresses in that netblock but others are located in North America and possible other places too, and similar geographic mapping services managed to get the location of the particular mail server (almost) right.

Although many open source and commercial mail filters rely on DNSBLs, there has been valid criticism, and even lawsuits against DNSBL operators. The main concern I have is that administrators may rely on a single DNSBL service to mark messages as spam and reject them without understanding the service's reliability and limitations.

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