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How Does Day Zero Anti-Spam Work In Practice?

By David Cawley | 4 minute read

Many of you will already be familiar with the concept of a Day Zero Virus attack. Whenever a new vulnerability is discovered, it’s likely that never-before-seen malware, without existing signatures, will start to appear. Given the danger of new attacks, AV vendors have developed various Day-Zero Anti-Virus solutions. For example, one e-mail security vendor delays messages with executable attachments for a number of hours to allow time for new AV signatures to be propagated.

The Anti-Virus companies are very aware that new virus campaigns will emerge, without signatures. They have solutions in place. However, in the world of Anti-Spam I don’t hear much discussion of new spam campaigns and what companies are doing to help protect their customer base against these attacks. A dip in effectiveness occurs when a new spam campign is launched and filters are not yet in place to block it i.e. Day Zero Spam! In February, we discussed the idea of “The Dip” with regard to AS effectiveness and I thought it worth further discussion.

Anti-Spam rules can be pre-emptive or reactive. For example, heuristic rules look for generic spam indicators in a message that could catch a small percentage of spam e-mail from new campaigns. However, spammers can easily setup drop boxes at many ISP’s to confirm successful delivery of the e-mail, before commencing the campaign. Reactive rules respond to active campaigns by creating targeted rules. Collected samples are required to write the rules against.

Typically, an Anti-Spam Operations center will have visibility into spam attacks via the use of honey pots to collect samples, as well as end user missed spam submissions. There’s a delay in the spam sample being reported to the operations center as it may take some time for the end user to report it. Also, the honey pot may not detect the message until long after the campaign has commenced. As the number of submissions to the center is huge, there’s a delay before the sample is prioritized to be processed by automated or human rule writers. Finally, after the rule has been created, there’s a delay in propagating the rule set to customers.

The scenario above is an optimistic one. In some cases, it may not even be possible to create an effective rule that doesn’t result in an increase in false positives. Think back to the crippling image spam attack over a year ago. So much legitimate corporate mail had images such as the company logo attached. It wasn’t easy to create rules. Anti-Spam effectiveness took a hit. Another example could be a customer in the Middle East using a US-centric Anti-Spam product. The operations center may not have enough visibility into localized samples of spam appearing in Arabic or Hebrew. The same can be said for customers in Asia.

For the most part, Anti-Spam vendors seem to keep very tight lipped on these deficiencies. Earlier this week, Cloudmark announced their new ActiveFilter. I should mention that they’re a partner of ours and we ship Traffic Control with Cloudmark. It’s pretty neat in that it actually scans the message store until the message is retrieved to see if any messages subsequently receive a spam verdict. The interesting thing is that this was the first time I’ve heard a major player in the AS market openly discuss the problem with new spam attacks:

The messaging security landscape has always been an arms race between attackers and anti-spam providers. In an effort to penetrate the inbox and reach their target audience, spammers and hackers are deploying extremely sophisticated techniques to evade spam filters. A current trend is to use botnets to send out huge volumes of rapidly-changing messages as quickly as possible. These bots can send millions of messages in under a minute. Given the intensity and speed of attacks, it’s no surprise that spam now constitutes more than 95 percent of all e-mail traffic and even with the most effective e-mail filtering in place, a small amount of spam will still find its way into e-mail inboxes––these are the messages spammers are banking on.

I’d love to hear how other Anti-Spam vendors are dealing with Day-Zero Spam Attacks? In the case of Traffic Control, we throttle never-before-seen connections until they build up a good reputation. A sender is guilty until proven innocent. Traffic shaping is agnostic to the message content. It doesn’t matter whether the spam message hides its content in images or Google Docs, or even if it is targeted in a language for a specific geographic region. I don’t believe in a silver bullet to combat spam in the short term, but I do believe in a layered approach. Use Traffic Shaping up front to protect the MTA, and a good content filter to further reduce spam.

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