"Surpassing one billion global users is a significant landmark in the history of the internet," said Magid Abraham, president and chief executive of comScore.
"It is a monument to the increasingly unified global community in which we live, and reminds us that the world truly is becoming more flat.
"The second billion will be online before we know it, and the third billion will arrive even faster than that, until we have a truly global network of interconnected people and ideas that transcends borders and cultural boundaries. "
ComScore's research suggests that the Asia-Pacific region accounted for the highest share of global internet users, taking a 41 per cent slice of the market. Europe takes second place with 28 per cent, followed by North America (18 per cent), Latin America (seven per cent) and Middle East & Africa (five per cent).
Although North America ranks third by region, the US still takes second place in the country rankings, accounting for 16.2 per cent of all internet users, beaten only by China with 17.8 per cent.
The UK takes fifth spot behind Japan and Germany, with 36.7 million unique visitors accounting for a 3.6 per cent share.
The research also revealed that Google continues to reign supreme in the online world, seeing 777.9 million surfers visiting its properties in December. This was followed by Microsoft and Yahoo with 647.9 million and 562.6 million respectively.
Social networking also continued to grow, according to the figures, and Facebook took the top spot in this category with a 127 per cent growth rate over the course of 2008.
Facebook also took seventh place overall behind AOL, Wikimedia Foundation Sites and eBay.
