They're probably in breach of contract too, I expect there is a click-through.
In the UK they could probably be got for "hacking" (ie cracking) as they are using the computer from which they download updates without authorisation and breaching a security feature in order to do so this puts them in contravention of the Computer Misuse Act (or at least on a naive reading, mine, it does so).
I'm sure many of these people are violating copyright to get a copy of the installer, but surely that can't be the main law being broken. Avoiding the specifics of Avast that I don't know, if they can get the installer from the producer, maybe because there's a trial, there can't be a copyright violation when no unauthorized copies are made, can it? So what is the exact law being broken?
In the UK they could probably be got for "hacking" (ie cracking) as they are using the computer from which they download updates without authorisation and breaching a security feature in order to do so this puts them in contravention of the Computer Misuse Act (or at least on a naive reading, mine, it does so).