"The ability to search for a person by phone number is intentional behavior and not a bug in Facebook," Facebook said Tuesday in an emailed statement. "By default, your privacy settings allow everyone to find you with search and friend finder using the contact info you have provided, such as your email address and phone number. You can modify these settings at any time from the Privacy Settings page."

"Facebook has developed an extensive system for preventing the malicious usage of our search functionality and the scenario described by the researcher was indeed rate-limited and eventually blocked," the company said. "We are constantly updating these systems to improve their effectiveness and address new kinds of attacks."

On Friday, independent security researcher Suriya Prakash publicly disclosed that Facebook's phone number search feature can be abused to find the name of people who own randomly generated phone numbers.

Facebook requires users to associate phone numbers with their accounts in order to gain access to additional features, including enhanced account security options like two-factor authentication. The website also allows users to locate other people's profiles by searching for their phone number.

However, without a strict limit on how many searches a user can perform, attackers could generate sets of thousands of sequential phone numbers and use the website's search feature to discover if any of them are associated with Facebook accounts.