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(2010-01-05) Y2k10 bug hitting us deemed... well... silly.

In 2000, the world let out a collective sigh of relief as the computer Armageddon, the feared result of the infamous Y2K bug, failed to appear. Ten years later, there are no signs of a big catastrophic failure either. But, our spam filter actually did suffer from an interesting bug. All mail received from unknown senders in 2010 has been given a higher spam-rating than expected. This has been fixed now.

Why is this? Well, spam Assassin checks the date in the received from headers on incoming email, and ranks dates in "the far future" with a higher spam score. But yesterday's future is today's today and the "far future" was every date from the 1st of January 2010.

So when 2010 finally arrived, all new email from unknown senders got an additional 3.2 spam points. A score higher than 4.0 is enough to put it in the junk mail folder.

Why it's not a big problem:
- Most mail comes from people you have previously mailed or replied to. The filter will not mark them as spam with the bayes filter.

- +3.2 is not a score that will automatically rank a message as spam. Most legitimate email have a negative score, so it's not that much of a problem.

- It's been fixed today, so it's at most 5 days worth of email that could have been tagged too high. I've not found any legitimate emails in my junk mail.

Here's the infamous bug in clear text:
Date =~ /20[1-9][0-9]/ [if-unset: 2006]

It's a regular expression matching dates after 2010.

The better code:
Date =~ /20[2-9][0-9]/ [if-unset: 2006]

Now we won't have a problem in the next ten years . History will repeat itself off course.

Official information from Spam Assassin's bug tracker

Posted: 2010-01-05 by Erik Zalitis
Changed: 2010-01-05 by Erik Zalitis

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