Last week at the country I live in there was an article in a newspaper with a list of people (journalists, businessmen, etc) that were being spied by the intelligence services of the country... They explained that this agency was spying all their whatsapp conversations, skype calls, cellphone calls, etc...

So when I read that I started to wonder HOW can they spy whatsapp conversations as they are over TLS, if they want to do a man in the middle attack they need to change the certificates in the device so they can attack the connection... is there another way??!?!?

This is a big surprise for me because I have nothing to hide, but I was happy just checking if the connections were https to feel secure as I thought that way nobody could see what I was sending/receiving (I know if they have access to the servers they can check anything but that's not a concern for me...)

And another question, how secure is to use Skype/Viber for calls? Is skype safer than a landline or cellphone line? Is telegram more secure than whatsapp?