This is a story on how you can use the “last seen” in WhatsApp and record it on your pc, even for strangers.
It’s interesting because the technology on how to perform this attack is quite simple, and it is not shown in details how this is performed (but it’s not too hard to reproduce). Instead, it is written as a story, on how you can find out the sleeping patterns of your friends (and strangers) and even if two people are dating or not.
It’s interesting how this is possible (even if you decide in your WhatsApp privacy account not to show the “last seen”) and what is the power of metadata even without knowing the full conversation.
A personal side-note: WhatsApp in encrypting end-to-end all the communication exchanged between the customers, but it is not encrypting this sort of metadata.