IBM has sent a letter to Twitter ahead of its IPO, but it wasn't to wish them a congratulations.

The letter that Twitter received from IBM was a notification that the company is alleging that the social network is infringing upon three of their patents, and will be looking to settle the matter. The patents in question, which were made known in Twitter's SEC filing on Monday, refer to "efficient retrieval of uniform resource locators [URLs]," a "method for presenting advertising in an interactive service" and "programmatic discovery of common contacts." Twitter's filing discloses that the company feels it can defend itself against IBM's allegations, but there's a possibility that IBM will be getting what it wants: shares of the company. Yahoo did the same against Google before they went public. "Based upon our preliminary review of these patents, we believe we have meritorious defenses to IBM’s allegations," the company said in their filing. "[However] there can be no assurance that we will be successful in defending against these allegations or reaching a business resolution that is satisfactory to us."

Twitter is set to go public either November 6 or 7, and shares have risen to $23 to $25. 

[via Mashable]