Two-step authentication will be introduced to make it harder for outsiders to gain access to an account, said the person, who declined to be identified because the information isn’t public. In addition to a password, the security measure usually requires a code sent as a text message to a user’s mobile phone, or generated on a device or software.

Twitter’s defense against hacks involving the theft of passwords came under scrutiny this week after a hacker sent a false post about explosions at the White House, triggering a drop in the Standard & Poor’s 500 Index that wiped out $136 billion in market value. The attack came the same month the U.S. Securities and Exchange Commission said companies can use social-media sites to share market-sensitive news. It also threatened to complicate efforts by Chief Executive Officer Dick Costolo to establish the service as a viable business ahead of a possible initial public offering.