Random musings on whatever subject strikes my fancy, published every other day.

Category: Geeky Stuff Page 4 of 52

Stupid Jeopardy! Category

The category of Final Jeopardy! for the last game of the All-Stars team tournament was “Constitutional Amendment Math”. I had a foreboding when I saw this, and it was right.

The clue asked the contestants to add the numbers of the Amendments banning state-sponsored religion, ending slavery and repealing Prohibition. The answer is 35, “cleverly” arranged so as to be a tribute to Jeopardy!’s 35-year run. (In its current incarnation, that is; the older Art Fleming version is typically “forgotten” by Trebek’s crew.)

Well, here’s why this set my teeth on edge. The numbers of the Amendments are not really quantities. We don’t do arithmetic with them, any more than we do with zip codes or phone numbers. They are just labels that happen to be numeric. If we’re making a spot for them in the memory of a program, or in a database, we should allocate text strings, not numbers.

This is a very important principle: I have seen a lot of applications errors that originated because labels were stored as numbers and then later, unintended consequences arose. For example, if we store all phone numbers as numbers, what happens if a future change causes them to be rounded? 9165551309 is not much more interesting or useful as a number than, say, 9.166 billion. But as a phone number, a label to a communication channel, its usefulness has been completely destroyed.

Deliberately doing arithmetic with these values just because all of them happen to be made up of digits? That is the kind of thing that screams out the sort of basic design error alluded to with phone numbers.

Getting Ready for BSides

BSides Rochester is tomorrow. The preparations are in their frantic final day.

Plus, today is a training day on CTF Basics, presented by The Hackerground.

Get a ticket to B-Sides if you don’t already have one, and be there tomorrow!

Free Stuff I Like

UptimeRobot is a free service for monitoring online properties: networks, websites, etc.  I use it for this blog and some others, and for my home network.  Tell it the website URL or network IP address / DNS name you want to monitor and it’s set up.  You can get notified by text message, email, RSS or a public web page that will be created for you.

A paid option is available that removes some limits (such as only 50 monitors) and adds features such as predefined maintenance windows or more frequent checking. For my use, the free option is fine so far: I have a grand total of six monitors active.

Speaking of monitoring your home network, there’s an important difference between most home networks and most commercial ones. Home networks typically have dynamic IP addresses, as opposed to the static IP addresses that are allocated to businesses. “Dynamic” means that the provider can change the IP address at their convenience, and with no notification. For many home uses it doesn’t matter because your IP address is not usually a destination, only a starting point. Netflix and Google can find you to provide the content you requested because they just send it back to where the request came from.

However, if you want to do something like monitoring your own home network, or hosting a web site from your own computer, now you have to be able to be a destination, just like microsoft.com. That means you need to claim an entry in DNS, the Internet’s “phone book”. But if your IP address can change without notice, it’s a problem: DNS entries always need an immutable destination address.

Enter Dynamic DNS. The principle is, a DNS entry is created for a location that has a dynamic IP address, and the location updates the DNS server with a new address whenever it changes. Most home routers have built-in support for this, you just have to choose a provider that supports one of the common methods of keeping updated. I use afraid.org because it’s easy to set up (step-by-step instructions for everything) and has proven 100% reliable. And the basic service is, of course, free. You select a domain from a long list (VERY long – see illustration), and then make up a new subdomain name for it. That subdomain becomes your very own DNS name, and you can give that out without worrying what happens when Comcast changes your IP address.

I’m going to do another post soon about some more free things I like: pfSense, Plex and Ubuntu. Meanwhile, check out Gizmo’s Freeware where you will find lots of free stuff for all your geekery needs.

Error Blast from the Past

I created the error message you see here at the Atom Smasher website, a fun site where you can exercise your own creativity and relive those cryptic and illogical error messages of yore.

This find is thanks to folks at Rochester B-Sides. Have I mentioned that yet this year?  Stay tuned!

Held for Ransom

He’s not a hacker, he’s a stock photo model

Today’s blog is at Safer Computing, about how your data can be held for ransom, and what you can do about it.


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