Countermeasures: 1. Sybil Attacks: Staking mechanisms or trusted hardware for identity; 2. Collusion: Random task assignment, blind evaluation, slashing penalties; 3. Incentive Design: Reputation systems to distinguish honest from malicious behavior. 对策包括：1. 女巫攻击：结合质押机制或可信硬件验证身份；2. 验证者合谋：随机分配任务、盲评估、Slashing惩罚使合谋收益为负；3. 奖励设计：引入信誉系统区分诚实与恶意行为。