There are now more than 225 million registered domain names, 5.9 million of which were added just in the fourth quarter of 2011, according to VeriSign Inc.’s latest Domain Name Industry Brief.

That works out to a growth rate of 2.7 percent over the third quarter of 2011, and marks the fourth straight quarter with greater than 2 percent growth.

Obviously most of those are either .com or .net, which together accounted for 113.8 million of those names. New registrations in those two top level domains totaled 7.9 million during the quarter, a 4 percent increase year-over-year in new registrations, with a renewal rate of 73.5 percent, up from 73.3 percent the previous quarter.

VeriSign also issued guidance about the growing problem of domain name hijacking, in which domain names are fraudulently transferred by password theft, hacking or – more commonly – by simply smooth-talking or scamming the information out of a person at the relevant company, a technique known as social engineering.

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Download VeriSign’s latest Domain Name Industry Brief here [pdf].

Photo of Langlands & Bell’s sculpture “Fifty Cities” by Flickr user querkmachine, used under Creative Commons license