Twitter is making changes to combat abuse and malicious automated accounts, including requiring more authentication for new users, in an effort to address complaints that social networking services have allowed harassment and manipulation.

Twitter is going to require confirmation of an email address or phone number to sign up for an account. Twitter said it would work with experts to make sure the changes don't harm users in high-risk environments where anonymity is important.

Twitter has already released a series of updates to clamp down on suspicious activity. Earlier this year, Chief Executive Officer Jack Dorsey acknowledged the San Francisco-based company inadvertently helped spread misinformation, harassment and manipulation via bots, or automated accounts. Last week, Twitter acquired security startup Smyte to help fight online spam, abuse and fraud.

"These issues are felt around the world, from elections to emergency events and high-profile public conversations," Twitter said Tuesday in a blog post. "As we have stated in recent announcements, the public health of the conversation on Twitter is a critical metric by which we will measure our success in these areas."

The company is also developing machine learning algorithms that proactively find problematic accounts, rather than waiting until someone flags the bad behavior.

Twitter is also reducing the visibility of suspicious accounts. A warning sign will be placed on these accounts, and new users will be unable to follow them.

The company said it's conducting an audit to ensure that every account created on Twitter has passed a security check to prevent automated signups.