11/13/2005

For rainy days

This is a lesson for rainy days that should be recorded properly.

It started without warning, and with forebodings of misfortune. About nine months ago, I checked my English blog site on my PC server, which is a kind of morning ritual then. Finding it inaccessible, I was utterly dumbfounded and expected the worst nightmarish scenario of my site having been hacked and destroyed. First, I checked my Linux server by 'df' command that shows the disk usage...

Two years ago, my first published Linux server with FTP capability was totally damaged by hackers overnight. It required only one night during which incessant disk writing sound had been continuing without end. When the sound ceased, I found the incredulous result that "0 (zero)" byte is available for use as the displayed result of 'df' command. That was so-called, famous "syn-flood" attack that fills "syn (chronous)" code in the free disk space that resulted in no space available for use. From that day, I studied security matters intently and did all possible counter-measures against malicious attacks on my Linux server.

Remembering this awful experience of two years ago, I watched the output of my 'df' command. To my great relief, this was not the case. No indication of any attacks by hackers so far. But I couldn't access the Internet from my Linux server. Internet connection was severed by some unknown reason. Because it was morning time before going out, I couldn't do anything at that time.

When returned from my office, I finished my two papers for presentation in Las Vegas this July by reflecting comments by Professor N who happens to be my adviser in my graduate school. So, I am a business person and at the same time a student of graduate school to get a doctor's degree! I submitted these two papers by using Conference Management System. After that I resumed my "mystery tour" of my disabled Linux server. By restarting network functions, soon I reached the Internet. So far, so good. I checked accessibility to my Linux server both within home LAN and from outside. When I'm inside my home LAN, I could access to the Linux server by specifying IP address directly, but to my great horror, the displayed content of my English blog was miserable whitewashed 'style.' Yes, no styles seemed to be applied on it! Oh, my! My supposed hacker infiltrated my blog and erased some formatting files? The incredible answer to this enigma was discovered next day.

My Linux server was alive and well. But my blog was not doing well. Why? My analysis told me that 'cube290.com' domain cannot be reached from outside of my private LAN world. I checked the expiration date of use of my private domain. It was set as June, 2006. Then I checked if my domain is active or not by Web page http://www.dnsreport.com/ , and it was also OK. At that time I remembered that I used one more Web service when opening my English blog: nifty dynamic DNS service. Soon I refreshed my IP address on the appropriate nifty page where nifty dynamic DNS service is provided. Refreshed information will require from one day to three days to be propagated over the Internet.

Next day, I confirmed that my English blog was alive and well. Very good!

This was the first time I experienced these type of problem since my first activation of Linux server. It was a good experience to refresh my Linux memory and to know the importance of saving operating resources of blogs for rainy days.

2005 11 13 [Linux server] | 固定リンク | コメント (0) | トラックバック