Setting Up Internal Security Reviews

An internal security review is a structured, team-based evaluation of your project's code, architecture, and operational logic. Unlike an external audit, it is conducted by your own developers and security engineers who have deep context about the system's intended behavior and business goals. The primary objective is to find and fix security flaws, logic errors, and potential attack vectors before the code is deployed to a testnet or, critically, to mainnet. This proactive approach is significantly cheaper and less damaging than responding to a post-exploit incident, which can cost millions in lost funds and reputational damage.

To establish an effective review process, you need a clear scope and methodology. Start by defining what will be reviewed: new features, upgrades to existing contracts, or changes to critical dependencies like oracles or bridge integrations. The methodology should combine manual code review—where engineers meticulously read through Solidity or Vyper code—with automated analysis using tools like Slither, Mythril, or Foundry's fuzzing capabilities. Manual review catches complex business logic flaws and integration issues, while automated tools efficiently identify common vulnerabilities like reentrancy, integer overflows, and improper access control.

The core of the review is the threat modeling and analysis phase. Reviewers should ask adversarial questions: What happens if a user supplies malicious calldata? Can funds be trapped in the contract? Are admin functions properly timelocked? A practical technique is to write specific test cases in Foundry that attempt to break the invariants of the system. For example, for a lending protocol, an invariant test would assert that the total borrowed assets can never exceed the total supplied collateral. Failing such a test immediately highlights a critical flaw. Documenting these threats and test cases creates a living security specification for the protocol.

Finally, integrate the review findings into your development lifecycle. All critical issues must be resolved before merging a pull request. Use a tracking system, like GitHub Issues or a dedicated security board, to log vulnerabilities, assign owners, and verify fixes. Establish a security champion role within the team to oversee the process and ensure consistency. The output is not just patched code, but also improved developer awareness and a stronger security culture, making each subsequent review more effective. This internal rigor is what separates robust, long-lasting protocols from those vulnerable to the next exploit.

Before writing a single line of code, define your security review scope. This includes specifying which assets require review: production smart contracts, governance modules, upgrade mechanisms, and key management systems. Establish clear severity classification for findings, such as Critical, High, Medium, and Low, aligning with industry standards like those from the Immunefi Vulnerability Severity Classification System. This framework ensures consistent prioritization and response to identified issues across your team.

Assemble a cross-functional review team with defined roles. At minimum, this includes the core development team, a dedicated security lead or internal auditor, and product managers. For smaller teams, implement a four-eyes principle where no code is deployed without review by at least one other qualified engineer. Document the review checklist covering common vulnerabilities: reentrancy, access control flaws, integer overflows/underflows, and logic errors. Tools like Slither or Mythril can automate parts of this checklist.

Integrate security tooling into your development lifecycle from day one. Set up static analysis in your CI/CD pipeline using Foundry's forge inspect or Hardhat tasks. Configure gas optimization and vulnerability detectors to run on every pull request. Establish a mandatory pre-deployment review gate that requires all automated checks to pass and a manual sign-off from the security lead for changes affecting core contract logic or funds. This creates a consistent, enforceable security barrier.

Create a secure development environment for testing. This involves deploying a mainnet fork (using tools like Foundry's forge create --fork-url or Hardhat Network) to simulate real-world conditions and interactions with other protocols like Uniswap or Aave. Maintain a comprehensive test suite with high branch coverage, focusing on edge cases and failure modes. Include fuzz testing (e.g., with Foundry's forge test --fuzz-runs) and invariant testing to validate system properties under random inputs and states.

Finally, establish clear documentation and communication protocols. Every contract should have a technical specification detailing its intended behavior, access controls, and upgrade path. Use NatSpec comments for on-chain documentation. Create a remediation workflow that defines steps for triaging, fixing, and re-auditing discovered vulnerabilities. Track all findings and decisions in a centralized system to build an institutional knowledge base and demonstrate due diligence to users and external auditors.

An effective internal review process begins with a clear scope and threat model. Define what is being reviewed: a new smart contract function, an upgrade to an existing protocol, or integration with a new oracle. Simultaneously, establish a threat model by asking: what are the valuable assets (user funds, governance power) and who are the potential adversaries (malicious users, competing protocols, MEV bots)? This dual focus ensures the review targets the code's most critical attack surfaces from the outset.

The core of the review is the checklist-driven audit. This is not a free-form code read but a systematic examination against known vulnerability classes. A robust checklist includes items for: reentrancy, access control flaws, integer overflows/underflows, oracle manipulation, front-running, and logic errors. For each item, reviewers should trace the relevant code paths, asking "what if" scenarios. Tools like Slither or Foundry's forge inspect can automate the detection of some issues, but manual review is essential for complex business logic.

Documentation is critical for accountability and institutional knowledge. Every finding should be logged in a standardized format, typically including: a unique ID (e.g., ISR-001), severity (Critical, High, Medium, Low), a clear description of the vulnerability, the affected code files and lines, and a proof-of-concept exploit scenario. Use a tracking system, from a simple shared spreadsheet to dedicated platforms like Jira or Linear, to manage the lifecycle of each finding from discovery to resolution and verification.

The final, non-negotiable phase is remediation and verification. For each finding, the development team must implement a fix. The security reviewer's role then shifts to verification: they must re-examine the patched code to ensure the vulnerability is fully addressed and that the fix does not introduce new issues. This often involves writing a specific test case in Foundry or Hardhat that demonstrates the exploit no longer works. Without this closed-loop process, the review's value is significantly diminished.

An internal security review is a mandatory pre-audit phase where your core development team systematically examines the codebase for vulnerabilities. This process is not a replacement for a professional audit but a critical filter that catches obvious bugs, logic errors, and design flaws early. It reduces audit costs, shortens the feedback loop with external firms, and demonstrates due diligence to users and investors. The goal is to enter an audit with a codebase that has already passed rigorous internal scrutiny, focusing the expensive external review on complex attack vectors and novel risks.

The process begins with documentation and specification review. Before a single line of code is examined, the team must verify that the technical specifications, architecture diagrams, and user flow documents accurately reflect the intended system behavior. Common pitfalls include mismatches between the whitepaper and the implementation, or undefined edge cases in state transitions. Use tools like Slither's printer to generate inheritance graphs and function summaries to ground the review in the actual code structure. This phase ensures everyone reviews against a single source of truth.

Next, conduct a line-by-line manual code review focused on security-critical components. This includes the core contract logic, any proxy upgrade implementations, privilege management functions (e.g., onlyOwner), and financial math. Look for classic vulnerabilities: reentrancy in withdrawal patterns, improper access control, integer overflows/underflows (even with Solidity 0.8.x, review unchecked blocks), and price oracle manipulation risks. Use a checklist derived from sources like the SWC Registry or Consensys Diligence's Smart Contract Best Practices. Review sessions should be collaborative, with at least two senior developers examining each module.

Following the manual review, run a suite of automated analysis tools. Static analyzers like Slither and MythX detect common vulnerability patterns, while formal verification tools like Certora or Scribble can prove specific properties about your code. Fuzzing with Echidna or Foundry's built-in fuzzer is essential for testing invariant properties under random inputs. For example, a test might assert that totalSupply always equals the sum of all user balances. Integrate these tools into your CI/CD pipeline to run on every pull request, but a dedicated run on the final release candidate is mandatory. Triage every finding, even false positives, to understand why the tool flagged it.

The final phase is scenario and integration testing. Deploy the entire system to a testnet or local fork (using tools like Anvil) and execute complex user journeys and attack simulations. Test for integration risks: how does the protocol behave if a critical DEX oracle fails? What happens during extreme network congestion? Use fork testing to simulate specific block states. Document every test case and its outcome. All findings from each phase must be logged in a tracking system (e.g., GitHub Issues), with severity ratings, fixes, and verification steps. This creates an audit trail that is invaluable for the external auditor and for post-audit maintenance.

A Continuous Integration and Continuous Deployment (CI/CD) pipeline automates the steps to build, test, and deploy code. For blockchain projects, integrating security reviews into this pipeline is non-negotiable. Manual audits are critical but slow; automated checks provide a first line of defense for every commit. By embedding tools like Slither, MythX, or Foundry's forge test into your pipeline, you can catch common vulnerabilities—such as reentrancy, integer overflows, and access control flaws—before they reach production. This practice, often called shift-left security, reduces risk and cost by identifying issues early in the development lifecycle.

Setting up an internal review starts with selecting the right tools for your stack. For Solidity projects, Slither offers static analysis with a low false-positive rate, ideal for fast feedback. MythX provides deeper, paid analysis using symbolic execution. If you use Foundry, you can integrate its native fuzzing and invariant testing directly. The core step is creating a pipeline configuration file (e.g., .github/workflows/security.yml for GitHub Actions or .gitlab-ci.yml). This file defines a job that installs the security tool, runs it against your contracts/ directory, and fails the build if vulnerabilities above a certain severity are detected. This enforces a security gate for all pull requests.

A basic GitHub Actions workflow for running Slither might look like this:

yamlCopy
name: Security Scan
on: [push, pull_request]
jobs:
  slither:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Run Slither
        uses: crytic/slither-action@v0.2.0
        with:
          target: './src'
          args: '--exclude-informational'

This configuration checks every push and PR, running Slither on the src folder and ignoring purely informational findings. The build will fail if any medium- or high-severity issues are found, blocking merging until they are resolved. You can extend this with steps to run unit tests, generate coverage reports, or even deploy to a testnet for integration testing.

For a comprehensive review pipeline, combine multiple tools. You might run Slither for static analysis, Ethlint (Solhint) for style and security rule checking, and Foundry fuzzing for dynamic analysis in a single workflow. It's also crucial to manage secrets securely. Use your CI/CD platform's secrets vault to store private keys for tools like MythX that require an API key, or for testnet deployment accounts. Never hardcode these values. Furthermore, configure branch protection rules in your repository settings to require the security check job to pass before a pull request can be merged, ensuring no code bypasses the automated review.

Beyond automated tools, integrate manual review checkpoints. Use the pipeline to generate standardized reports (SARIF, Markdown) and post them as a comment on the pull request. This gives human reviewers clear, actionable context. For critical protocol upgrades or new core contracts, mandate a manual audit stage in the pipeline that pauses deployment until a senior developer approves. This hybrid model—automated gates for common issues and scheduled pauses for deep review—balances speed with security. Documenting this entire process, including tool configurations and review responsibilities, is key for team onboarding and maintaining security standards as your project scales.

Establishing a formalized internal security review is not a one-time project but an ongoing discipline. The goal is to create a repeatable, documented process that integrates security into your development lifecycle. This includes defining clear review criteria, assigning ownership to a security champion or team, and scheduling regular cadences (e.g., pre-audit, post-major update). Tools like a standardized checklist, a dedicated repository for findings, and a severity classification system (Critical, High, Medium, Low) are essential for consistency and tracking.

Your next steps should focus on automation and continuous improvement. Integrate static analysis tools like Slither or Mythril into your CI/CD pipeline to catch common vulnerabilities early. Use property-based testing frameworks such as Foundry's fuzzing capabilities to simulate unexpected inputs and states. Regularly update your review checklist based on new attack vectors, lessons from public exploits, and feedback from external auditors. Documenting and reviewing near-misses internally is as valuable as analyzing successful attacks.

Finally, foster a culture of security ownership across your entire engineering team. Security should not be siloed with a single reviewer. Encourage all developers to understand common pitfalls like reentrancy, oracle manipulation, and gas optimization errors. Consider conducting internal workshops or code walkthroughs using historical vulnerabilities from platforms like Rekt.news. The most secure protocols are built by teams where every member is empowered to question assumptions and identify risks in the code they write and review.