# Attacks/Cheats/Weaknesses of Shards
### Chain Control
1. **Hijack the main chain**: the main chain controller can manipulate the main chain block to control the process of sampling eligible collator.
2. **1% sharding attack**: if the sampling process fails to select with high randomness, it’s possible for an attacker to start 1% attack in the shard: if there are 100 shards, the attacker can focus on attack one particular shard, they only need 1% hash rate (PoW)/deposit (PoS) to control the shard.
3. **30% sharding attack**: [ERP#1340](https://ethresear.ch/t/30-sharding-attack/1340)
4. **DoS attacks**: [ERP#1048](https://ethresear.ch/t/state-execution-scalability-and-cost-under-dos-attacks/1048) - slight influence???
Note that the proposer-collator separation scheme is no longer planned for in-protocol use as per this post: [Exploring the proposer/collator split](https://ethresear.ch/t/exploring-the-proposer-collator-split/1632). Instead a proposer/notary scheme is planned as per [this post](https://ethresear.ch/t/a-general-framework-of-overhead-and-finality-time-in-sharding-and-a-proposal/1638) and [this post](https://ethresear.ch/t/a-minimal-sharding-protocol-that-may-be-worthwhile-as-a-development-target-now/1650).
1. [Proposing-collating separation scheme] **Proposer withholding attack**: the proposer griefs collators by not revealing collation bodies.
2. [Proposing-collating separation scheme] **Collator stealing proposer’s fee**: the collator might be able to tamper `proposer_address` and `proposer_signature` of the proposal.
3. [Proposing-collating separation scheme] **Proposer reversion bribes**: the proposer offers collations with high fees that are off of the canonical chain, thereby offering a clear bribe to build on top of a secondary chain, with the goal of reverting transactions.
### Stateless Client and Access List
1. **Censorship**: stateless client model loses censorship resistance
1. **DoS executors by reverting**: Allowing cross-shard transactions and state execution to happen faster than finality means that executors can be forced to redo all their work on all shards if only one shard suffers a short-range reversion.
1. **Loose finality in loosly coupled fork choice rule**: in loosely coupled fork choice rule, it's even harder to have a more explicit finality on shard chain than PoW main chain.