The term "Big brother is watching" means,the informations and the data are not secured for us.

Everyday our data is going outside.For example,we are using various social medias.So,to log into it,we need to login.So we are giving them access to take our informations and data.And they are taking our data.We don't have enough privacy. 

So,basically our data is not secured.As much new technology are coming, data is being unsecured.People are knowing our information by technology. 

So,This is called Big brother is watching me.