Damaged WEB pages or pages that impersonate legitimate pages inform the victim that the computer has been blocked due to the discovery of malware on the computer. The user is asked to call the "toll free" number for assistance. There may be an audio file indicating that the computer is infected. Do not be tempted and close the page immediately.
More details at the link - https://www.symantec.com/blogs/threat-intelligence/tech-support-scam-call-optimization