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Author: steve

Brief DBL false positive

A code glitch in a new DBL sub-zone known as 'Abused-Legit' caused the new Abused-Legit zone to list ".net." for 60 minutes from 08:35 UTC. — The Spamhaus Project (@spamhaus) December 17, 2014 Spamhaus are rolling out a new subzone of the DBL, for domains whose webservers have been compromised and used to host spam […]

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Lorem Ipsum for PII

When you’re developing code to handle data it’s almost essential to have a decent sized set of test data, so you can build a test harness to check on functionality and performance as you go. A common way of doing that is to take a snapshot of your production database and pull out an appropriate subset […]

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Friendly email addresses

Most of the time when we’re talking about email addresses, we’re talking about the actual user@domain format that’s used to send mail over the wire, but that’s not how we most often see them. When they’re used in a To: or From: header they’re usually associated with a display name – the “real name” of the […]

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STARTTLS and misplaced outrage

About a month ago someone posted a heavily elided screenshot that they claimed was evidence of their ISP, AT&T, sabotaging SMTP connections being sent over their network, meaning that anyone could sniff their passwords and traffic. This is it:     Most email people looking at that saw the asterisks in the banner and went […]

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Bounces at Verizon

There have been lots of reports of Verizon rejecting valid email addresses for a few hours this morning. They seem to have fixed things now but you probably want to make sure you didn’t suppress those addresses.

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SWAKS: the SMTP Swiss Army Knife

SWAKS is a general purpose testing tool for SMTP. For basic SMTP testing it’s a more convenient, scriptable alternative to running a transaction by hand, but it also lets you test things that are difficult to do manually, such as authentication or TLS encryption. It’s a perl script that installs fairly easily on OS X […]

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I can’t click through if you don’t exist

Recipients can’t click through if you don’t exist A tale of misconfigured DNS wrecking someone’s campaign. I got mail this morning from A Large Computer Supplier, asking me to fill in a survey about them. I had some feedback for them, mostly along the lines of “It’s been two decades since I bought anything other […]

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DMARC and report size limits

I just saw an interesting observation on the dmarc-discuss mailing list. Apparently some of the larger providers who are implementing DMARC for inbound email may not be handling some of the grubbier corners of the spec perfectly. That’s not surprising at all – early adopters tend to deploy code that implements early versions of the […]

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Alice and Bob and PGP Keys

Last week Alice and Bob showed how to cryptographically sign messages so that the recipient can be sure that the message came from the purported sender and hasn’t been forged by a third party. They can only do that if they can securely retrieve the senders public key – which means they need to retrieve […]

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Alice and Bob Sign Messages

Alice and Bob can send messages privately via a nosy postman, but how does Bob know that a message he receives is really from Alice, rather than from the postman pretending to be Alice? If they’re using symmetric-key encryption, and Bob is sure that he was talking to Alice when they exchanged keys, then he already knows […]

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