Unsubscribing from mailing lists is hard. How many times have you seen a message "please remove me from this list," followed by two or three more pointing out that the instructions are in the footer of every message, followed by three or four more asking people to not send their replies to the whole list (all sent to the whole list, of course,) perhaps with a final message by the list manager saying she's dealt with it? more
A few days ago I was startled to get an anti-spam challenge from an Earthlink user, to whom I had not written. Challenges are a WKBA (well known bad idea) which I thought had been stamped out, but apparently not. The plan of challenges seems simple enough; they demand that the sender does something to prove he's human that a spammer is unlikely to do. more
There's a lot of argument as to which "anti-spam" techniques are legitimately so called. In this article, I'd like to consider what constitutes an anti-spam technique in an ideal sense, then consider the various practiced approaches to spam mitigation in that light, drawing conclusions as to how we should frame the "anti-spam" discussion. ...For the purposes of this discussion, let "spam" refer to "unsolicited bulk email". Not everyone agrees on this definition, but it's by far the most widely accepted, and without a working definition we won't be able to define "anti-spam"... more
RHEL6/Centos6 (and presumably RHEL7/Centos7) machines with the latest openssl packages now refuse SSL connections with DH keys shorter than 768 bits. Consider RHEL6 sendmail operating as a client, sending mail out to a target server. If the target server advertises STARTTLS, sendmail will try to negotiate a secure connection. This negotiation uses openssl, which will now refuse to connect to mail servers that have 512 bit DH keys. The maillog will contain entries with "reject=403 4.7.0 TLS handshake failed". more
Stepping back from the DMARC arguments, it occurs to me that there is a predictable cycle with every new e-mail security technology... Someone invents a new way to make e-mail more secure, call it SPF or DKIM or DMARC or (this month's mini-fiasco) PGP in DANE. Each scheme has a model of the way that mail works. For some subset of e-mail, the model works great, for other mail it works less great. more
Phil Zimmerman's Pretty Good Privacy (PGP) and its offspring have been encrypting and decrypting email for almost 25 years -- but require enough knowledge and determination to use them that adoption has never taken off outside the technoscenti. Now initiatives from several quarters aim to fix that -- but will it all "just work," and will end users adopt it even if it does? more
I have often remarked that any fool can run a DNS-Based Blacklist (DNSBL) and many fools do so. Since approximately nobody uses the incompetently run black lists, they don't matter. Unfortunately, using a DNSBL requires equally little expertise, which becomes a problem when an operator wants to shut down a list. When someone sets up a mail server (which we'll call an MTA for Mail Transfer Agent), one of the tasks is to configure the anti-spam features, which invariably involves using DNSBLs. more
DMARC is extremely useful, yet I've heard some vendors are putting their implementations on hold because of the IETF DMARC working group. You really shouldn't wait though -- it's been in wide use for nearly three years, enterprises are looking at DMARC for B2B traffic, and the working group charter is limited in it's scope for changes. Let's compare this to a similar situation in the past. more
The EFF has just posted a shallower than usual deeplink alleging an "email encryption downgrade attack" by ISPs intent on eavesdropping on their customers. They, along with VPN provider Golden Frog, have additionally complained to the FCC reporting this. Here, they've just noticed something that's common across several hotel / airport wifi networks... more
DMARC is what one might call an emerging e-mail security scheme. It's emerging pretty fast, since many of the largest mail systems in the world have already implemented it, including Gmail, Hotmail/MSN/Outlook, Comcast, and Yahoo. DMARC lets a domain owner make assertions about mail that has their domain in the address on the 'From:' line. It lets the owner assert that mail will have a DKIM signature with the same domain, or an envelope return (bounce) address in the same domain that will pass SPF validation. more
One of the hottest topics in the email biz these days (insofar as any topic is hot) is how we will deal with mail on IPv6 networks. On existing IPv4 networks, one of the most effective anti-spam techniques is DNSBLs, blackists (or blocklists) that list IP addresses that send only or mostly spam, or whose owners have stated that they shouldn't be sending mail at all. DNSBLs are among the cheapest of anti-spam techniques since they can be applied to incoming mail connections without having to receive or filter spam. more
Everyone who's been in the e-mail biz long enough knows the term FUSSP, Final Ultimate Solution to the Spam Problem, as described in a checklist from Vern Schryver and a form response that's been floating around the net for a decade. FUSSPs fall into two general categories, bad ideas that won't go away, and reasonable ideas that are oversold. more
Back in the dark ages of email delivery the only thing that really mattered to get your email into the inbox was having a good IP reputation. If your IP sent good mail most of the time, then that mail got into the inbox and all was well with the world. All that mattered was that good IP reputation. Even better for the people who wanted to game the system and get their spam into the inbox, there were many ways to get around IP reputation. more
It is surprisingly difficult to get accurate figures for the amount of spam that is sent globally, yet everyone agrees that the global volume of spam has come down a lot since its peak in late 2008. At the same time, despite some recent small decreases, the catch rates of spam filters remain generally high... A world in which email can be used without spam filters is a distant utopia. Yet, the decline of spam volumes and the continuing success (recent glitches aside) of filters have two important consequences. more
If you haven't been reading the news of late, venerable anti-spam service Spamhaus has been the target of a sustained, record-setting Distributed Denial-of-Service (DDoS) attack over the past couple of weeks... Of course, bad guys are always mad at Spamhaus, and so they had a pretty robust set-up to begin with, but whoever was behind this attack was able to muster some huge resources, heretofore never seen in intensity, and it had some impact, on the Spamhaus website, and to a limited degree, on the behind-the-scenes services that Spamhaus uses to distribute their data to their customers. more
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