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September 2014: The Month in Email

September was another busy month for us, but Steve stepped up and wrote a number of really interesting posts on email history, cryptography, and current technical issues in the email landscape.
We started the month with a look at the various RFCs that served as the technical specifications for developing message transfer protocols in the 1970s. It’s really fascinating to look at the evolution of these tools we use every day 40 years later. We followed up with a second post on the origins of network email, which is a great primer (or refresher) on the early days of email.
Steve’s four-part series on cryptography and email started with an in-depth look at how the industry is evolving with respect to encryption and privacy issues. He then introduced us to Alice and Bob (or reintroduced those of us who have been following the adventures of the first couple of cryptography), and described symmetric-key and public-key encryption. His next post described message signing, and how DKIM is used to manage this. He finished up the series with a post on PGP keys.
In industry news: Spamcop is shutting down its email service. There shouldn’t be any major impact on senders, but the post has some specific notes on DMARC implications. We also noted an interesting mail routing suggestion on Twitter, and wrote a post on using Mail.app for this.
In other DMARC news, we wrote about DMARC and report size limits, which might be useful information, depending on your configuration. We also launched a new DMARC tool to help senders understand who is publishing DMARC. Let us know what you think and if you’re finding it useful.
We couldn’t let a month go by without mentioning filters. We looked at a sector we don’t usually discuss, corporate filtering, and went in-depth on a much-misunderstood topic, content filtering.
Finally, Laura offered a webinar on a favorite topic, deliverability, in conjunction with the AMA and Message Systems. If you missed it, you can watch the recorded version here, or just take a peek at some of the reaction via Twitter.

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Another security problem

I had hoped to move away from security blogging this week and focus on some other issues. But today I see that both CAUCE and John Levine are reporting that there is malware spam coming from a Cheetahmail customer.
Looking at what they shared, it may be that Cheetahmail has not been compromised directly. Given mail is only coming from one /29, which belongs to one customer it is possible that only the single customer account has been compromised. If that is the case, then it’s most likely one of the Cheetahmail users at the customer got infected and their Cheetahmail credentials were stolen. The spammer then gained access to the customer’s Cheetahmail account.  It’s even possible that the spammer used the compromised customer account to launch the mail. If this is the case, the spammer looked exactly like the customer, so most normal controls wouldn’t have noticed this was a spammer.
This highlights the multiple vectors these criminals are using to gain access to ESPs and the mailing systems they use. They’re not just trying to compromise the ESPs, but they’re also attempting to compromise customers and access their accounts so that the spammer can steal the ESPs hard won and hard fought sending reputation.
Everyone sending mail should be taking a long, hard look at their security. Just because you’re not an ESP doesn’t mean you aren’t a target or that you can get away with lax security. You are also a target.

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Thoughts on filters

One of the questions we received during the EEC16 closing keynote panel was why isn’t there a single blocklist that everyone uses and why don’t ISPs share data more. It would be so much easier for senders if every ISP handled mail the same as every other. But the world isn’t that simple, and it’s not always clear which mail stream is spam and which is good mail.

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