David Xia

Author Archives: David

Making History

2012-02-20T14:46:33+00:00 | By

Final paper submission on December 12, 2009 for Columbia University’s Nonfiction Workshop class.

China has a long history of forgetting its past. When intellectuals criticized the first emperor in 213 BCE for burning classical books that could undermine his rule, he buried them alive. Two millennia later, Mao Zedong told throngs of teenage Red Guards to incinerate genealogical books, shatter antique pottery, and kill intellectuals during the Cultural Revolution. Political leaders saw China’s traditional culture as a backwater, and remembering was not important. Despite this cultural destruction, much has survived, and much more has been revived. In the summer… more...

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15 Ways to Increase Your WordPress’ Security

2012-02-19T18:51:10+00:00 | By

1. Don’t Display Error Messages on Failed Login

WordPress’ admin screen displays “ERROR: Invalid username.” if you enter an invalid username. But if you enter a valid username and an incorrect password, it’ll say “ERROR: Incorrect password.” This basic security flaw tells intruders which usernames to target. I don’t understand why the WordPress team designed it this way.

You can disable the error message by putting this in your theme’s functions.php:

add_filter(‘login_errors’,create_function(‘$a’, “return null;”));

2. Publish Posts as a Non-Admin User

Create a WordPress user that has admin privileges and publish all posts… more...

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Hear TV Show Characters Say a Quote – Playing With Twilio

2012-02-15T16:59:11+00:00 | By

I was inspired by Rob Spectre’s Laugh-o-tron and made a telephony extension to my Twitter Bots.

Try it out. Call 646-480-6046 to talk to various TV show characters. Right now the vast majority of the quotes are spoken by a text-to-speech program because I have to find, crop, and upload audio files for each one. But McNulty from The Wire (choice #1) has a few real audio clips. Let me know how I can improve it… more...

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8 Ways to Defend Against Brute Force SSH Attacks

2012-02-19T04:06:22+00:00 | By

I looked at my server’s auth logs today and was unsettled to find thousands of lines like these:

Feb 12 06:49:52 localhost sshd[25416]: Invalid user photo from xxx.xxx.xxx.xxx
Feb 12 06:49:52 localhost sshd[25416]: pam_unix(sshd:auth): check pass; user unknown
Feb 12 06:49:52 localhost sshd[25416]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=some.random.domain
Feb 12 06:49:54 localhost sshd[25416]: Failed password for invalid user photo from xxx.xxx.xxx.xxx port 49608 ssh2

I was looking at someone running a brute force attack on my server trying to gain SSH access. Looking further back in the logs, I found crackers (not… more...

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How to Send Email with Postfix on Ubuntu via Gmail SMTP

2012-02-16T17:40:04+00:00 | By

I just setup email sending on my server by following this clear tutorial.

The tutorial walked me through setting up Postfix on an Ubuntu server and sending email via Gmail’s SMTP. I had to create a certificate, sign it, have my server communicate via some secure transport layer with Gmail using another certificate signed by some country in South Africa. I don’t understand all of it, but it works.

If you have WordPress installed like me, you can test Postfix is working by asking for a… more...

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Redesign

2012-02-09T14:44:53+00:00 | By

I just finished redesigning my site. It was a lot more work than I expected. After becoming interested in Swiss design, both philosophically and aesthetically, I was inspired by the personal websites of Rdio and Django designer Wilson Miner, former New York Times web designer Khoi Vinh, and an Argentinian designer.

So I took elements from all three and combined them with my own tastes for minimalism, grids, and readability. At first I… more...

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The Origin of the World Wide Web

2012-02-04T19:35:20+00:00 | By

I’m reading Tim Berners-Lee’s book Weaving the Web about how he conceived of and designed the world wide web.

For a long time I never really got the distinction between the “Internet” and the “world wide web.” To me they were the same thing, and they might be for many other folks too. But in hindsight this is just a testament to how successful Berners-Lee’s creation is.

Most people’s perceptible interaction with the Internet is through a browser where they visit a website. The Internet is simply a… more...

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How the Internet’s Domain Name System Works

2012-02-12T22:45:24+00:00 | By

So what exactly happens when you type “davidxia.com” into your browser’s address field and hit “Enter”?

A website is simply a collection of online content ranging from text documents to images to video. All this content lives in physical machines called servers. Servers listen for incoming calls or requests from web browsers or applications and respond with the appropriate content.

Think of the Internet as having a giant Yellowpages phone book

So how does this content get from a machine that could be halfway around the world to your computer? Every machine that’s connected to the Internet… more...

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College Isn’t and Shouldn’t Be the Best Years of Your Life

2012-01-07T17:50:52+00:00 | By

“College will be the best four years of your life.”

If you’re a high schooler, someone’s probably told you this. If you’re an adult, you’ve probably said this to some impressionable young person. If you think this sentence is bullshit and at worst a harmful sentiment to say or hear, you’re with me.

Imagine a statesman declares to his country’s citizens, “The best years of our country are going to be the next four years.” I would think, “So you’re implying that it’s all downhill after that?” That’s essentially what adults are telling young people when they say… more...

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What Do Venture Capitalists Do All Day?

2012-02-09T16:47:45+00:00 | By

I just listened to a great episode of Stanford Technology Ventures Program’s Entrepreneurship podcast. This one has Kleiner Perkins Caufield & Byers partner Dana Mead explaining what venture capitalists do as an industry, as individuals in their day to day life, and how he decides where to invest.

Mead’s talk is very informative. Here are some of my biggest takeaways. He said VC were originally a small, boutique industry but are now an asset class. The change from 1980 to 2006 has been more than a ten-fold increase. Mead said this was driven by university… more...

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