USA and Brazil battle for title of top spam-relaying nation

Amidst all the hubbub and activities around International Kill-A-Zombie Day on Halloween, and Paul Ducklin determining that there are 80,000 zombies in Australia, one interesting piece of data may have been overlooked.

Every three months Sophos publishes it’s “Dirty dozen” list of top spam-relaying countries. This is an easy way to tell which countries are sending out the most spam from compromised computers (also known as zombies) acting as part of a botnet.

Here’s the latest “Dirty dozen” which we put together at the end of last week, looking at July – September 2009:

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Remember that the owners of these computers probably have no idea that their PC (and it usually is a PC, although we do come across compromised Linux and Mac computers too) has been hijacked by a hacker and is silently sending out spam on behalf of the spammers.

Once again, America rules the roost – although Brazil is coming up fast and could potentially overtake the USA by the end of the year.

What’s most remarkable to me is how China has fallen down the chart over the last few years. It used to be way up there, rivalling the USA for the dubious title.

But make sure you don’t fall into the trap of thinking that only these 12 countries are to blame for the spam arriving in your inbox – in total we counted over 230 different countries relaying spam during the quarter.