Spam email may sound like a modern annoyance, but it actually dates back to 1978 when a marketer mass-emailed what was then called ARPANET (the pre-cursor to the modern Internet). Today, spam is both a burden -- clogging inboxes with unwanted junk mail -- and a threat for its capacity to spread viruses and cyber malware. Thanks to the Internet's global scope, spam is also a global threat. Spam 'botnets' in one country can pump out billions of message that plague inboxes around the world. According to Cisco, in just one day (March 26), there were 155,000,000,000 spam messages sent worldwide. Though spam email has been on the decline thanks to more effective email filtering, it's still a headache. In a mid-year report on the stuff, Sophos' senior technology consultant Graham Cluley put the phenomena in perspective: "Spam emails make up an average of 45-50 percent of corporate email -- that is one unwanted, unsolicited message for every important communication!" In its 2013 Security Threat Report, SophosLabs surveyed the world of spam emails and found 10 countries that generated the most spam.