Social media website Twitter paid $36 million (£21.5 million, AU$39.5 million) to buy patents from IBM, according to a recent filing with the US Securities and Exchange Commission.

The document notes that the microblogging website acquired 900 patents from IBM in December. The announcement was subsequently made in January, but the financial details of the transaction were not revealed.

Interestingly, the filing shows why Twitter bought the patents in the first place: to avoid a legal dispute with IBM over the possible infringement of three or more of its patents.

Patent shield

Of course, there is a big leap between three patents and the 900 it eventually bought, but the move does give it the potential for future development, as well as added security in the legal standing of its existing services.

Twitter now has 956 patents, according to Bloomberg, and 100 patent applications awaiting approval in the US Patent and Trademark Office. Before the company went public last year it had just nine patents, which made it vulnerable to intellectual property lawsuits.

"We presently are involved in a number of intellectual property lawsuits, and as we face increasing competition and gain an increasingly high profile, we expect the number of patent and other intellectual property claims against us to grow," Twitter revealed in the filing.