Twitter Inc. is adding a new security tool to its website, making it harder for hackers to gain access to accounts after last month's false Associated Press tweet triggered a stock market decline, Bloomberg reported. The two-step authentication measure requires users to input a code sent by text message to a mobile phone in order to log in. The extra security feature is optional, but this Mashable article makes the argument that businesses should implement it. On the other hand, this article in The Wall Street Journal (subscription required)  warns that the verification process could make it harder for brands that have multiple people tweeting from multiple computers.