Category Archives: Technology

Protecting domains from spammers

Spammers quite often ‘spoof’, or fake, the from address of an email.

As a result of this, many unsuspecting domain owners are being ‘blamed’ for spam that appears to come from their domain.

Fortunately, there is a relatively easy way to protect your domain from this: Publish DMARC policies.

If you are publishing SPF records and signing your email with DKIM, you can publish DMARC policies that tell receiving mail servers what do with emails that don’t align with the SPF and DKIM information.

SPF policies are DNS records that indicate what mail servers your mail is sent from.

DKIM is a way to add digital signatures to your email so that receiving mail servers can verify it was sent from an authorized source and that it wasn’t modified in transit.

Now what if you have a domain that you NEVER send email from?

Protecting those domains from being used in spam is even easier.

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LetsEncrypt certbot and Lightsail

Although not directly supported, it’s quite possible to use the LetsEncrypt certbot client on Amazon Lightsail Linux.

First of all … what is LetsEncrypt?

Let’s Encrypt is a free service that offers basic SSL certificates any web site.  The certificates are good for 90 days but can be renewed indefinitely. With the proper software, the installation & renewal of the certificates can be fully automated.

There are a few things to be aware of and workarounds that need to be done.

First, download the certbot-auto client itself…

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Amazon Lightsail


Ha! I’ll be you thought this blog was dead.

Well, truth be told, it was pretty close … but you never know when inspiration will strike.

So a little while ago I had a hardware failure on one my servers. This incident has given me the incentive to try and move some of the servers I host to other machines … where I don’t have to worry about the hardware end of things.

To that end, I started looking at hosting providers.  One of the providers I’m looking at is Amazon Lightsail.

Amazon Lightsail provides micro instances of their AWS compute service at very good prices.

A 512mb / 20gb Linux instance only costs $5 / month and the first month is free.

So I’ve been playing around with that and like it a lot.

I’ve currently got a handful of sites moved over to Lightsail.

I have encountered a few gotcha’s though …

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Confirming cancel in a ProgressMonitorDialog

I’m working on a routine that downloads content from a host to the users desktop.

As the content is being downloaded, a progress dialog is displayed (implemented as ProgressMonitorDialog).

In the progress monitor, the cancel button is enabled.

In the default implementation, if the cancel button is pressed on the ProgressMonitorDialog, the cancel button is disabled.

I wanted to be able to ask the user if they really want to cancel the operation. If they don’t, then continue on with the operation. If they do, then perform the cancellation as usual.

I couldn’t find a straight forward way to implement this with the default operation, so I came up with my own solution…

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Mailbait Threats

Back in October of 2012 I devised a way of blocking abuse of my mailing list server by detecting mailbait abusers (mailbait.info offers a ‘service’ to fill your, or someone else, mailbox with unwanted mailing list subscriptions). In June of 2013 I refined the technique.

Basically I detected if someone was visiting the mailing list subscribe page from mailbait.info and sent them to a special page that also annoyed them by popping up hundreds of javascript alerts about not spamming people.

Regardless of the popups, people still try to use mailbait to involuntarily subscribe people to my lists (well, try at least, my lists require a closed loop confirmation system).

Today I received the following threat from a mailbait.info user ..

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I’m inclined to ignore the ‘warning’ … but I find it somewhat satisfying that my approach has annoyed someone sufficiently.

As an added measure, I’ve updated my system security mechanism to block any IP that attempts to use the mailbait service more than once.

Dynamically populating a Combo based on shift key

In a recent project I had a combo box that I wanted to add additional entries to if they clicked on it with the shift key pressed.

This is to allow to select entries that would not normally be displayed (for example, out dated values that could actually be selected).

To do this, I added key-up & key-down listeners on the Display object and populated the Combo based on the shift key state.
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