Ex-Hong Kong resident and flamboyant internet mogul Kim Dotcom said he was considering legal action against tech giants such as Twitter, Google and Facebook for infringing copyright on a security measure he invented. Dotcom, who is on bail in New Zealand as US authorities seek his extradition in the world's biggest copyright case, said he invented "two-factor authentication", which has been adopted by many major websites. Twitter became the latest major player to introduce the measure on Wednesday following a series of cyberattacks that saw hackers take over the accounts of high-profile targets such as media organisations and send out fake tweets. Twitter introduces Two-Step-Authentication. Using my invention. But they won't even verify my Twitter account?! "Twitter introduces Two-Step-Authentication. Using my invention. But they won't even verify my Twitter account?!" Dotcom tweeted. "Google, Facebook, Twitter, Citibank, etc. offer Two-Step-Authentication. Massive [intellectual property] infringement by US companies. My innovation. My patent." The 39-year-old posted a US patent describing the authentication process filed in 1998 by Kim Schmitz, Dotcom's name before he legally changed it, and published in 2000. Dotcom said he had never sought to enforce copyright on his invention but was now reconsidering in light of the US case accusing him of masterminding massive online piracy through his now-defunct Megaupload file-sharing site. The authentication process works by sending a text message containing a verification code to the user's cellphone when they log in that must be entered to gain access to the account.