Rice's Theorem makes the Ken Thompson hack impossible in general. He only executed his hack in a single short-term demonstration against a specific target, but

Rice's Theorem makes the Ken Thompson hack impossible in general. He only executed his hack in a single short-term demonstration against a specific target, but it's not possible to make a "long-con" against an open-source project with lots of activity and lots of people building it even if you find a way to infect nearly all of those people.