Category Archives: IT Operational Excellence

The IT Detective Agency: Cognos stopped working

Intro Here’s another in our continuing exciting IT drama. A user reports that her Cognos app stopped working. She’s in charge of the Cognos application servers, I run the Cognos gateway on a Linux server. I have almost no working … Continue reading

Posted in Admin, IT Operational Excellence, Linux, SLES | Tagged , | 1 Comment

The IT Detective Agency: the case of the messages from mars

Intro Today we got a “funny” message on our SLES 11 server in the /var/log/warn file. You might think that Martians have landed! The Details Specifically this: Nov 9 10:54:19 drjohn24 kernel: [72397.088297] martian source 10.120.2.24 from 10.0.0.3, on dev … Continue reading

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Apache Tips in Light of Security Problems

Intro I am far from an expert in Apache. But I have a good knowledge of general best practices which I apply when running Apache web server. None of my tips are particularly insightful – they all can be found … Continue reading

Posted in Admin, Apache, IT Operational Excellence, Linux, Security, Web Site Technologies | Tagged , , , , , , | 1 Comment

The IT Detective Agency: ARP Entry OK, PING not Working

Intro Yes, the It detective agency is back by popular demand. This time we’ve got ourselves a thriller involving a piece of equipment – a wireless LAN controller, WLAN – on a directly connected network. From the router we could … Continue reading

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Internet Service Providers Block TCP Port 22 or Do They?

Intro The original premise of this article is that some Internet Service Providers were seen to block TCP port 22, used by ssh and sftp. However, as often happens during active IT investigations, this turns out to be completely wrong. … Continue reading

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The Basics of How to Work with Cipher Settings

December, 2014 Update With some tips for making your server POODLE-proof, and 2016 update to deal with OpenSSL Padding Oracle Vulnerability CVE-2016-2107 Intro We got audited. There’s always something they catch, right? But I actually appreciate the thoroughness of this … Continue reading

Posted in Admin, Apache, IT Operational Excellence, Security | Tagged , , , , , , , , , , , , , , , , , , , , | 17 Comments

Splitting a Text File Into Two Lines with Awk

Intro How do you split a text file into two lines output per one original input line? Of course there are zillions of ways, with shell, xargs, Perl, your favorite tool, etc. But I decided to revisit that old standard … Continue reading

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The IT Detective Agency: How We Neutralized Nasty DNS Clobbering Before it Could Bite Us

This gets a little involved. But if you’re the IT expert called on to fix something, you better be able to roll up your sleeves and figure it out! In this article, I described how some, but not all ISPs … Continue reading

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DNS Clobbering – How ISPs Twist DNS Replies

Intro Some ISPs have taken advantage of missing or broken DNS records, using them as an excuse to guide users to their own pages. From an Internet purist’s point-of-view this is bad behavior. I call it DNS clobbering. In my … Continue reading

Posted in DNS, IT Operational Excellence | Tagged | 2 Comments

How to Stop Chinese Spam – for Mail Admins, w/ June 2014 update

(Updated 12/19/2011 and 6/2014 with additional character sets) (updated 9/2012 with additional signature) Intro I have been a target for random Chinese language spam in my various email accounts, but the problem has really gotten worse in the past few … Continue reading

Posted in Internet Mail, IT Operational Excellence, Spam | Tagged , , , , , , , | 14 Comments