Blockchain Security Audit vs Smart Contract Audit: What’s the Difference?

Startup and enterprise teams often conflate “smart contract audits” with “blockchain security audits.” They’re not the same. This guide dissects the scope, outputs, and decision criteria—updated for 2025 realities like EIP‑4844 blobs, rollup “training wheels,” and account‑abstraction changes—so you choose the right engagement at the right time.

A blockchain security audit covers the entire on‑chain and off‑chain system (infrastructure, keys, bridges, rollups, governance). A smart contract audit focuses on contract code and protocol logic. In 2024–2025, most losses stem from infrastructure/key compromise, so many teams need both—sequenced correctly.

TL;DR for decision‑makers

Choose a Smart Contract Audit (SCA) to eradicate code‑level defects, verify protocol invariants, and harden upgrade paths.
Choose a Blockchain Security Audit (BSA) to assess end‑to‑end risks: keys (MPC/HSM), nodes/RPC, L2/bridge assumptions, governance/timelocks, monitoring/IR, MEV exposure, and data availability.
In 2024, attackers stole ~$2.2B; the majority was driven by infrastructure (key and front‑end) attacks—60–80% in multiple datasets—so don’t stop at code review. (chainalysis.com)

Why the distinction matters more in 2025

Ethereum Dencun (EIP‑4844) changed L2 data flows with blob transactions, a separate blob‑gas market, and KZG commitments that rely on a trusted setup—great for fees, but a new operational surface to monitor. (eips.ethereum.org)
Optimism’s OP Mainnet shipped permissionless fault proofs (Jun 10, 2024), moving OP Stack chains to Stage 1 decentralization—this affects withdrawal trust assumptions you must explicitly validate in audits. (docs.optimism.io)
Rollup maturity is now tracked via L2BEAT’s Stages (0→2); your risk posture depends on where your L2 sits and the powers of its Security Council and upgrade timelocks. (l2beat.com)
Account‑abstraction proposals like EIP‑7702 (Pectra‑era candidate) change EOA behavior and break some tx.origin‑based assumptions—auditors must test for these edge cases. (eips.ethereum.org)

Definitions you can act on

Smart Contract Audit (SCA)

A code‑centric review of your protocol contracts (Solidity/Vyper/Rust), including:

Threat modeling for protocol logic and integrations (DEXs, price oracles, bridges).
Static/dynamic analysis mapped to SWC Registry categories and OWASP/EEA standards. (github.com)
Property‑based testing, fuzzing, invariant testing, and (where justified) formal verification. (foundry-book.zksync.io)
Upgradeability risk review (transparent/UUPS/beacon proxies), admin surface, and timelock/governance controls. (docs.openzeppelin.com)

Primary deliverable: prioritized findings with SWC/SCSVS/EthTrust mapping, exploit proofs of concept, fixed‑code review, and regression test artifacts. (entethalliance.org)

Blockchain Security Audit (BSA)

A system‑level assessment across:

Key management (custody, wallets, signers), node/RPC infra, CI/CD, monitoring, incident response.
Economic/security assumptions for L2s, bridges, and DA layers; sequencer and fault/validity proof posture; exit windows. (l2beat.com)
Governance (multisigs, Security Councils), upgrade procedures/timelocks, and end‑user MEV protection options. (openzeppelin.com)

Primary deliverable: an actionable risk register and a remediation plan spanning on‑chain patches and off‑chain controls.

2024–2025 breach data: why “code‑only” is not enough

2024 hacks totaled about $2.2B; many incidents were infrastructure‑led (private keys/seed compromise, front‑end hijack). TRM and Chainalysis both highlight infrastructure attacks dominating losses. In H1‑2025 alone, >80% of stolen funds came from infrastructure attacks. (chainalysis.com)

Implication: even a clean contract codebase can be drained via compromised deployer/admin keys, malicious upgrades, DNS hijack, or compromised RPC front‑ends. Your audit scope must reflect that reality.

Scope: what each audit type actually checks

Smart Contract Audit: concrete scope checklist

Logic/Invariant correctness: ERC‑20/ERC‑721/AMM math, solvency, fee accounting, invariant preservation. Verified via fuzz + invariant suites (Foundry) and select formal rules (Certora). (foundry-book.zksync.io)
Known class coverage: SWC categories (reentrancy, auth misuse, unchecked calls), SCSVS controls. (github.com)
Upgrades: proxy pattern selection, storage layout diffs, UUPS _authorizeUpgrade access control, timelock strategy, and rollback/rehearsal. (docs.openzeppelin.com)
External dependencies: oracles, L2 messaging, router approvals, token permit flows; failure‑mode tests.
Gas/DoS limits: bounded loops, griefing vectors, reentrancy guards, emergency pause semantics.
Chain‑specific:
- Ethereum AA readiness: tx.origin anti‑patterns under EIP‑7702‑style flows. (eips.ethereum.org)
- Solana programs: ensure upgrade authority is properly removed for immutability where intended. (solana.com)

Tools you should expect to see used (representative): Foundry (fuzz/invariants), Slither, Echidna, Manticore/Mythril, and optionally Certora Prover for high‑impact properties. (foundry-book.zksync.io)

Blockchain Security Audit: concrete scope checklist

Key management & custody
- Signers in HSMs (FIPS 140‑3 L3) or MPC with threshold policies; rotation, quorum, and emergency revoke procedures. (csrc.nist.gov)
Node/RPC & mempool posture
- Multi‑provider RPC with health checks; tested fallbacks; use of private‑orderflow RPC (Flashbots Protect) to mitigate sandwiching. (isdown.app)
MEV mitigation for end‑users
- Enable private routing or batch auctions (e.g., CoW Protocol, UniswapX), and consider rebate‑program RPCs like MEV Blocker. (docs.cow.fi)
L2/bridge assumptions
- Check rollup “Stage” (0/1/2), presence/permissions of proof systems, exit windows, Security Council powers, DA bridge upgradeability. (l2beat.com)
Solana/Cosmos operational posture
- Solana: BPF upgradeable loader usage; verify upgrade authority custody or revocation. Cosmos: validator KMS with YubiHSM/Ledger, double‑sign protection. (solana.com)
Monitoring/IR
- On‑chain monitoring with Forta detection bots; operational alerting/automation via Defender Monitor (or successors). (docs.forta.network)

Practical examples (the “new details” you can use this quarter)

1) Ethereum + L2 rollup dApp (OP Stack or Base)

Confirm fault proofs are live on the target chain; OP Mainnet activated permissionless proofs on June 10, 2024. If you rely on permissioned withdrawals or a Security Council, that is a material trust assumption to document in your risk register and user docs. (docs.optimism.io)
Use L2BEAT’s Stages to set policy: Stage 1 systems should have ≥7‑day exits for non‑Council upgrades; Stage 2 requires permissionless proving and ≥30‑day exits. Audit governance contracts and timelocks accordingly. (l2beat.com)
If your rollup posts blobs to L1 (EIP‑4844), add blob‑gas trend dashboards and near‑DA‑outage runbooks; blob parameters and KZG commitments are distinct from calldata. (eips.ethereum.org)

2) Upgradable EVM protocol migrating to UUPS

Enforce multi‑sig + timelock on upgrade rights; validate storage layout compatibility in CI (OpenZeppelin Upgrades). Explicitly test downgrade and rollback. (docs.openzeppelin.com)
Red‑team the upgrade path: attempt a malicious implementation swap and prove the defense (e.g., timelock delay observed on‑chain). Document a “break‑glass” path.
Track admin key custody in HSM/MPC with quorum; simulate signer loss and rotation. (csrc.nist.gov)

3) Solana program launch

If program immutability is a product requirement, revoke the upgrade authority after deployment and evidence it on‑chain; many programs remain upgradeable by default under the BPF upgradeable loader. (solana.com)
If you must retain upgradeability, harden the authority (HSM or ledger‑backed custody) and drill two‑person control with a documented, rehearsed runbook. (docs.cosmos.network)

4) Cosmos app‑chain integrating IBC + CosmWasm

Treat IBC as trust‑minimized, not trustless: if a counterparty’s validator set exceeds the BFT fault threshold, the Tendermint light client can be deceived; misbehaviour proofs freeze the client but can’t fix full capture—plan rate limits and incident responses. (ibc.cosmos.network)
Run validators with KMS (YubiHSM or Ledger app), separate hosts, and double‑sign protection; verify ed25519 support. (docs.cosmos.network)

Emerging best practices to add to your 2025 playbook

Private orderflow + MEV rebates: route user transactions via Flashbots Protect or MEV Blocker where suitable. MEV Blocker reported 4,079 ETH in user rebates in 2024—set this up as a default path for retail flows. (docs.flashbots.net)
Batch auctions over FCFS: CoW Protocol’s fair combinatorial batch auctions and UniswapX’s auction‑based flow reduce sandwichability versus public mempools. Add these venues to routing logic. (docs.cow.fi)
Storage‑aware invariant fuzzing: enable Foundry’s storage layout output to power smarter invariant input sampling; run long‑horizon campaigns with afterInvariant hooks to close positions and assert solvency. (foundry-book.zksync.io)
Formal verification for high‑impact invariants: Spec and prove key rules (no balance underflow, conserved supply, monotonic accrual) using Certora Prover; wire into CI with rule‑level gating. (docs.certora.com)
Rollup stage gates: codify go‑live criteria tied to L2BEAT Stage 1/2 requirements (e.g., permissionless proofs present, ≥7/30‑day exit windows). (l2beat.com)
Blob‑era observability: separate dashboards for blob gas utilization and DA health; include alerting for blob‑sidecar propagation anomalies introduced post‑Dencun. (eips.ethereum.org)

Deliverables and evidence you should demand

For SCA
- A threat model and a mapping of findings to SWC/SCSVS/EthTrust controls, with exploit proof/PoC and reproducible Foundry test artifacts. (github.com)
- Invariant test suite + fuzz harnesses committed to your repo; optional formal specs for critical invariants (Certora CVL). (docs.certora.com)
- Upgrade path review including on‑chain governance and timelock rehearsals. (docs.openzeppelin.com)
For BSA
- A complete key‑lifecycle playbook aligned to FIPS 140‑3, with signer HSM/MPC evidence and rotation drills. (csrc.nist.gov)
- RPC resilience test results and an MEV policy (private routing defaults; supported relays/builders). (docs.flashbots.net)
- L2/bridge risk matrix tied to L2BEAT stages (proof system status, exit windows, Security Council powers). (l2beat.com)
- Monitoring runbooks with Forta/Defender setups (alerts, auto‑responses, escalation paths). (docs.forta.network)

Red flags we still find (and how to fix them fast)

Single‑key upgrade admins on UUPS proxies; fix with Safe multisig + timelock and verify _authorizeUpgrade guards. (docs.openzeppelin.com)
No private‑orderflow routing; enable Flashbots Protect or MEV Blocker and monitor sandwich rates before/after. (docs.flashbots.net)
L2 dependency without proof system clarity; document proof availability and exit windows, and set caps/pauses gated on stage upgrades. (docs.optimism.io)
Solana program left upgradeable unintentionally; revoke authority and store the transaction evidence. (solana.com)

What 7Block Labs recommends as a sequence

Pre‑audit readiness (1–2 weeks)

Align on scope: contracts vs infra vs rollup/bridges.
Turn on observability: Foundry test coverage; blob/DA dashboards if relevant; Forta bots for privileged events. (docs.forta.network)

Smart Contract Audit (parallelizable, 2–6 weeks depending on size)

Threat model + SWC/SCSVS baseline; fuzz/invariants integrated in CI; targeted formal proofs for high‑impact rules. (github.com)

Blockchain Security Audit (2–4 weeks)

Key/RPC/L2/bridge deep dive; governance + timelocks; MEV routing; incident response table‑top. Include DA/rollup assumption validation post‑Dencun. (eips.ethereum.org)

Fix‑verify and go‑live controls (1–2 weeks)

Re‑run tests, enact governance/timelocks, finalize MEV/private RPC defaults, and lock Solana programs if needed. (docs.flashbots.net)

Buyer’s checklist: ask your auditor these questions

Can you show prior reports mapping to SWC/SCSVS/EthTrust, with reproducible Foundry/Certora artifacts? (owasp.org)
For L2 deployments, how will you evaluate proof systems, exit windows, and Security Council powers (L2BEAT Stages)? (l2beat.com)
Do you assess DA/Blob metrics post‑EIP‑4844 and propose monitoring SLOs? (eips.ethereum.org)
What’s your key‑management baseline (FIPS 140‑3, MPC), and do you test signer rotation/failure? (csrc.nist.gov)
Do you provide MEV mitigation guidance (private orderflow, batch auctions, rebate RPCs) with measurable before/after KPIs? (docs.flashbots.net)

Appendix: concrete tools and commands to adopt today

Run long‑horizon invariants with storage‑aware fuzzing:
- foundry.toml:
```
extra_output = ["storageLayout"]
```
- After‑campaign accounting in
```
afterInvariant()
```
  to assert solvency. (foundry-book.zksync.io)
Formal verification entry point (example):
- ```
certoraRun MyToken.sol --verify MyToken:MyToken.spec
```
  and gate PRs on key rules. (docs.certora.com)
Mainnet‑fork pre‑deploy rehearsals:
- ```
anvil --fork-url <ARCHIVAL_RPC>
```
  to test migrations and upgrades against real state. (getfoundry.sh)
MEV‑aware routing defaults:
- Offer Flashbots Protect and/or MEV Blocker as a one‑click wallet RPC option; track rebates and sandwich deltas. (docs.flashbots.net)

Bottom line

Smart Contract Audits prove your code’s safety and correctness, but 2024–2025 data shows attackers more often target keys, admins, front‑ends, and rollup/bridge assumptions. Pair SCAs with a Blockchain Security Audit to protect the whole system and your users. (chainalysis.com)
Bake in private orderflow, batch auctions, strong key custody, and L2 stage‑aware governance before launch. Your security story—and your attack surface—now spans well beyond Solidity files. (docs.flashbots.net)

If you want a scoping call, 7Block Labs can review your repo and architecture in 48 hours and propose a right‑sized combination of SCA + BSA aligned to your chain(s), L2s, and go‑live timeline.

References used for select facts and figures:

EIP‑4844 (Dencun): blob transactions and parameters; KZG commitments. (eips.ethereum.org)
OP Stack fault proofs live on OP Mainnet (Jun 10, 2024). (docs.optimism.io)
L2BEAT Stages framework (0/1/2). (l2beat.com)
EIP‑7702 impacts (EOAs acting as contracts; tx.origin pitfalls). (eips.ethereum.org)
2024–2025 hack data (TRM, Chainalysis, Reuters). (trmlabs.com)
OpenZeppelin Upgrades guidance. (docs.openzeppelin.com)
SWC Registry and OWASP SCSVS. (github.com)
Flashbots Protect overview. (docs.flashbots.net)
MEV Blocker metrics and CoW/UniswapX auction mechanisms. (mevblocker.io)
Solana program upgrade authority and loaders. (solana.com)
Cosmos KMS and validator security. (docs.cosmos.network)