As part of its first quarterly financial report as a publicly traded company, Facebook announced last week that it had 955 million monthly users worldwide. But does that tell the entire story? Perhaps not.

In a new and required filing made to the US Securities and Exchange Commission, Facebook admitted that 8.7 percent of its user base may have "fake" accounts on the service. That amounts to over 83 million of Facebook's monthly user base.

These fake accounts fall into three categories. One of them is duplicate accounts. In its filing, Facebook says they may account for 4.8 percent of its monthly user base. A person who has more than one Facebook account is in violation of the company's terms of service and Facebook says these still happen "despite our efforts to detect and suppress such behavior."

Another 2.4 percent of Facebook's subscriber base could have what the company calls "user-misclassified accounts". These happen when someone creates a personal profile for a business or organization, or for someone who wants to make a personal account for a pet or other "non-human entity."

Finally, yet another 1.5 percent of accounts are termed as "undesirable". Facebook says these subscribers create accounts "that we determine are intended to be used for purposes that violate our terms of service, such as spamming."

Source: SEC.gov