1-855-707-0817 is a fake "Yahoo Support Team" customer service telephone number. The fake support number is being used by cybercriminals to trick potential victims into calling it. If potential victims call the number, the cybercriminals will ask them for their Yahoo account credentials(usernames and passwords). If the requested information is given to the cybercriminals, they will use it to gain access to their potential victims' account, hijack and use them fraudulently.
The cybercriminals may even ask their potential victims to give them remote access to their computers. If they do so, the cybercriminals will secretly steal their personal or even financial information from their computers. Or, silently use their computers to commit other cybercrimes.
Online users who have already called the fake technical support number and who have been tricked by the cybercriminals are asked to change their passwords immediately before their accounts are hijacked and used fraudulently.