Smart Contract Audit Basics: What Every Builder Should Know
Smart Contract Audit Basics
Deploying unaudited smart contracts with real funds is one of the fastest ways to lose them. Audits don't guarantee safety, but they dramatically reduce known vulnerability classes before mainnet.
Common vulnerability classes
Reentrancy
An external call before state update lets an attacker re-enter and drain funds. Use checks-effects-interactions and reentrancy guards.
Integer overflow/underflow
Solidity 0.8+ has built-in checks, but custom assembly and unchecked blocks can still bite you.
Access control
Missing onlyOwner or role checks on sensitive functions. Always map every external/public function to a threat model.
Oracle manipulation
Price feeds from a single DEX pool can be flash-loan manipulated. Use TWAPs, multiple sources, or Chainlink.
Preparing for an audit
- Freeze the codebase — no feature changes during audit
- Write comprehensive tests — aim for high branch coverage
- Document invariants — what must always be true?
- Provide a threat model — who are the actors and what can they do?
- Run static analysis — Slither, Mythril, Foundry fuzzing
The audit process
A typical engagement:
| Phase | Duration | Output |
|---|---|---|
| Scoping | 1–2 days | Scope doc, timeline |
| Review | 1–4 weeks | Findings report |
| Remediation | 1–2 weeks | Fixes + retest |
| Report | final | Public or private report |
Severity ratings: Critical → High → Medium → Low → Informational.
Post-audit
- Fix critical and high findings before launch
- Consider a bug bounty program
- Monitor on-chain activity with alerting
- Plan upgrade paths if using proxies
Key takeaway
Security is a process, not a checkbox. Audits catch what humans and tools find at a point in time. Ongoing monitoring and responsible disclosure matter just as much.