In its latest S-1 amendment filing with the Securities and Exchange Commission, Twitter said it had been sent a letter by IBM claiming it had infringed “at least three” of its patents held in the US.

In the correspondence, IBM invited Twitter to negotiate a “business resolution” for the alleged misuse. “The three patents specifically identified by IBM in the letter were U.S. Patent No. 6,957,224: Efficient retrieval of uniform resource locators, U.S. Patent No. 7,072,849: Method for presenting advertising in an interactive service and U.S. Patent No. 7,099,862: Programmatic discovery of common contacts,” Twitter said in its updated filing.

Twitter believes it has “meritorious defenses” for these alleged patent infringes, but cannot guarantee that it could successfully defend their use in court.

“From time to time we may introduce new products and services, including in areas where we currently do not have an offering, which could increase our exposure to patent and other intellectual property claims from competitors and non-practicing entities,” Twitter added.

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