Why Traditional DDoS Protections Fail Against Blockchain Networks

Attackers spammed the sequencer with millions of low-fee transactions, exploiting its first-come-first-served mempool to create a ~4-hour backlog. The network remained 'live' but unusable, as validators couldn't keep up with posting data to L1.

• Problem: Traditional rate-limiting fails; the sequencer must accept all valid, paying txns.
• Solution: Implemented priority gas auctions and dynamic basefee to economically disincentivize spam.

A spam program created ~1 million new token accounts per day, exploiting low rent-exemption costs (~0.002 SOL) to bloat validator state. This caused memory exhaustion and degraded network performance for all users.

• Problem: DDoS targets state storage, not just network bandwidth.
• Solution: Increased rent costs and implemented state compression via Merkle trees to reduce the cost of spam.

Bots execute self-referential contract calls that consistently fill blocks, artificially inflating the EIP-1559 base fee. This creates a feedback loop, pricing out real users while the attacker profits from MEV extraction in the same blocks.

• Problem: Attack is economically rational and protocol-compliant.
• Solution: No clean protocol fix; relies on PBS (Proposer-Builder Separation) and crLists to separate block building from inclusion.

An attacker deployed hundreds of malicious subnets, each requiring validation from the Primary Network. This consumed ~30% of the Primary Network's consensus bandwidth, slowing cross-subnet messaging and threatening liveness.

• Problem: Shared security model creates a cascading resource drain.
• Solution: Introduced subnet resource pricing and stake-weighted validation duties to align costs with externalities.

Traditional web servers can block IPs or require CAPTCHAs. On-chain, the only cost is gas. Spammers can generate infinite wallets and pay trivial fees to flood the mempool, crippling transaction ordering and finality for legitimate users.

• No Identity: Pseudonymous wallets provide no persistent reputation to blacklist.
• Sybil-Resistant: Attackers can spin up thousands of wallets for pennies.
• Target: Mempool: Congestion here delays all transactions, not just the spammer's.

Spam isn't just about traffic; it's about forcing the network to store worthless data forever. Every calldata byte on Ethereum or storage write on Solana increases the permanent state size, raising hardware requirements for nodes and threatening decentralization.

• Permanent Cost: Nodes must store spam data indefinitely.
• Resource Exhaustion: Targets the network's most constrained resource: global state.
• Protocol-Level: Mitigation (e.g., EIP-4444) requires hard forks, not config changes.

The Proposer-Builder-Separation (PBS) model centralizes transaction filtering into a few builder relays. Spamming the mempool can manipulate block building algorithms, extract value via time-bandit attacks, or simply DoS the relay infrastructure itself, creating a single point of failure.

• Centralized Chokepoint: Attack ~10 major relays to disrupt Ethereum block production.
• Algorithmic Manipulation: Spam can bias builder logic for maximal extractable value (MEV).
• Ineffective Filtering: Builders are financially incentivized to include high-fee spam.

Rollups batch transactions to save costs, but their sequencers are vulnerable to the same spam vectors. A spam attack on Arbitrum or Optimism can stall the entire chain, while fraud/validity proofs add computational overhead that spam can exploit.

• Sequencer DOS: A single centralized sequencer is a trivial target.
• Proof Overload: Spamming invalid transactions forces costly proof generation.
• Bridge Congestion: Spam on L1 can paralyze L2 withdrawal bridges like Optimism Portal.

Traditional defenses rely on tracking connection state, but blockchain nodes process millions of stateless, unsigned packets from anonymous peers. A firewall sees valid consensus gossip as an attack, creating a false positive rate >90% that cripples network liveness.

• Key Benefit 1: Protocol-layer rate limiting (e.g., libp2p's identify protocol) authenticates peers before accepting traffic.
• Key Benefit 2: GossipSub's mesh scoring in networks like Solana and Polygon penalizes bad actors without centralized blacklists.

Cloudflare-style IP blocking is useless when an attacker spins up 10,000+ node instances on AWS or botnets for ~$5k. The attack surface is the protocol's P2P layer itself, not a single IP.

• Key Benefit 1: Proof-of-Work for network access, like Ethereum's eth/65 protocol, imposes a ~5-10ms CPU cost per connection to slow sybil creation.
• Key Benefit 2: Stake-weighted peer selection, as seen in Celestia's data availability layer, makes flooding the network economically prohibitive.

CDNs absorb bandwidth attacks, but blockchain DDoS targets CPU, memory, and disk I/O with cheap, valid transactions. A $50k spam attack on Solana (2021) or $1 spam on early Avalanche can stall consensus by filling mempools and bloating state.

• Key Benefit 1: Dynamic base fees (EIP-1559) and prioritization markets create a native economic filter for network access.
• Key Benefit 2: Separate execution/consensus clients and modular data layers (e.g., EigenDA) isolate resource exhaustion to specific components.

The only scalable defense is making attacks economically irrational. This requires protocol-native cost functions for every network action, from sending a transaction to connecting a peer.

• Key Benefit 1: Staked peer-to-peer networks like Polygon Avail use bonded validators to slash malicious relay behavior.
• Key Benefit 2: Transaction pricing that scales super-linearly with demand, as theorized for suave chains, prevents cheap spam during congestion.

Move from connection-centric to intent-centric peer management. Nodes should advertise and subscribe to specific data (blocks, txs, attestations) rather than accepting all gossip, drastically reducing wasted bandwidth.

• Key Benefit 1: Ethereum's Req/Resp protocol and topic-based subscription in GossipSub reduce irrelevant traffic by ~70%.
• Key Benefit 2: Light clients and zk-proofs of state (like Succinct) allow trust-minimized data retrieval without syncing the full chain.

DDoS parameters must be governance-upgradable and fork-resistant. Emergency measures like increasing gas limits or adjusting peer scoring weights should be executable via DAO vote or validator supermajority.

• Key Benefit 1: Cosmos SDK's on-chain governance allows rapid parameter tuning in response to live attacks.
• Key Benefit 2: **Optimism's ** fault-proof system and Arbitrum's BOLD challenge protocol can pause and validate state transitions under duress.