Is there a way to flag block this type of behavior?
Longer answer: Basic data analysis can pick up most if not all the shenanigans. Doesn't matter how much they "age" the accounts or hide their tracks, eg IP address etc. Don't even necessarily need high powered hardware or even machine learning. They do help in particular ways if you choose to use them.
Fake vote detection is now a choice not to rather than a technical blockage.
This does come with a need to specify a filter.
Or, a sort and aging scheme.
But then we get upvote mobs, hello reddit.