Any clues or advice welcome!

A few days ago I decided to update my MBP and install OS X Mavericks. Since doing so, I've had several problems with ransomware, you know the one - Police Attention... . no problem 'Force Quit' and start again. However, my wife's iphone and my son's school notebook (running Windows 8) have had the same problem. Not so good as the consequences for my son when attempting to use his notebook at school have deeply embarrassed him.
Anyway, to cut to the chase, both my son's school and my wife's computer 'friend' have claimed that there is something wrong with our router, and that it's probably due to me updating my MBP. Admittedly, this has all happened since the update but I knowingly accept any changes to my router's config. to enable the update.
Any clues as to what could be going on, or how I've upset my router would be appreciated. I live in Spain, don't speak too much Spanish and feel I might used as a scapegoat. So I need something to fight back with if there is anything.
Cheers in advance!

Three things to download as Ransomware etc come from recent downloads.

1. AdBlock plus.

2. ghostery.

3. Adware Medic.

Neither the router nor the update to Mavericks is the cause of your "Ransom ware". The cause of that is simply something you or someone downloaded or a site that was visited and should not have been.

Download, install, and run: AdwareMedic.app

Thanks for your advice h and c. Duly noted and followed but this did nothing for me. `In fact, the ransomware became more a problem, hence my delay in thanking you.
Anyway, I ended up resetting Google and have since added your recommended apps etc. It seems to have done the trick for the time being, but let's see what happens when my wife and son get home... and, yes, my wife's computer 'friend' is coming to check the router.
Ciao for now.