Avoiding Unwanted Phone Calls (São Paulo)
I am using the following method to avoid annoying and possible malicious phone calls. By annoying I mean telemarketing, and by malicious I'm referring to those calls where people try to ask you for personal data or randsom money for a bogus abduction of someone you know.
Anyway I simply avoid answering phone calls from people who are not listed as contacts by my cell/mobile phone and then enter the phone number registered to the the missed call into the top right hand corner box located in the page linked below.
You can see if the phone number you received the call from is associated by the police to any criminal activity and/or if other users have complained about the same number ( see the comments below the result).
Another way to do this is by entering the area code plus phone number in a google search. This is faster since it will display if the number appeared in the list compiled by Protected content but you will probably have to follow the link to see exactly what kind of iillegal or annoying activity that number has or is being used for.