I have recently heard a few independent rumors about massive collusion amongst reviewers in major AI/ML conferences. The way this works is that a large group of program committee (PC) members start a chat group (on WhatsApp/Telegram etc.) and share their assigned papers; other members of the group flag papers that are theirs and get the "insiders" to score them higher.
To make things concrete, Alice and Bob start a chat where both share their assigned papers. Alice sees that Bob's batch contains one of her papers, and asks Bob to write a glowing review of that paper.
Are these rumors substantiated? Has anyone else heard of this going on? If it is as widespread as I was led to believe, what does this mean for the review process in these conferences and what countermeasures can we take?