Block Stuffing Attack

1 min read

Pronunciation

[blok stuhf-ing uh-tak]

Analogy

Like stuffing a mailbox with junk mail so the postman can’t deliver legitimate letters efficiently.

Definition

A denial‑of‑service tactic where an attacker fills blocks with spam or low‑value transactions to bloat size, increase , and slow network processing.

Key Points Intro

stuffing exploits size/gas limits to degrade performance and extract .

Key Points

Spam TX: Floods mempool with many small or complex transactions.

Fee manipulation: Bids minimal fees to fill blocks, forcing others to overpay.

Network congestion: Increases propagation time and orphan risk.

Resource exhaustion: Drives up storage and computation costs for nodes.

Example

An attacker submits thousands of zero‑value transfers with minimal , causing blocks to reach limits and delaying genuine transactions.

Technical Deep Dive

Attack scripts use pools to bypass per-address limits, broadcast via to ensure inclusion. They optimize size to maximize usage per byte. Nodes experience high GC pressure on trie updates and increased processing time.

Security Warning

stuffing can lead to elevated user and potential chain splits if nodes lag; implement per‑address rate limits and dynamic pricing.

Caveat

Mitigations like EIP‑1559 dynamic reduce incentives but do not eliminate risk entirely.

Related Terms

Mempool

Gas Limit

Flashbots

Blockchain & Cryptocurrency Glossary

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