Implement Robust Monitoring Security Rules
Monitoring is a critical component of smart contract security. While extensive audits and formal verification help secure contracts before deployment, monitoring ensures ongoing security and operational integrity. Real-time tracking of the on-chain state helps detect anomalies, prevent exploits, and mitigate damage in case of unexpected behaviors. Additionally, code issues are sometimes discovered after deployment. For immutable smart contracts, monitoring is often the only way to mitigate these issues, making it an essential tool for maintaining security in a live environment.
Effective monitoring involves two key categories of rules: generic security rules and tailor-made security rules. Generic rules cover common security scenarios such as detecting abnormal balance changes or tracking failed transactions.
However, tailor-made rules are equally important. These custom rules address unique aspects of a specific contract’s logic and risk profile, providing more targeted protection. Security researchers play a vital role in defining these rules during the security review of the code, leveraging their understanding of the contract’s structure and potential vulnerabilities to create a monitoring strategy that complements pre-deployment security efforts.
How to Implement Monitoring Security Rules
Define Security Rules: Create clear, actionable conditions to monitor. These should align with the contract’s purpose, logic, and risk profile.
Use Reliable Tools: Leverage blockchain analytics platforms, event listeners, or custom-built monitoring solutions.
Automate Alerts: Set up automated notifications for violations of predefined security rules.
Regularly Update Rules: As your contract evolves or as new threats emerge, refine your monitoring logic to stay effective.
Examples of Generic Security Rules
1. Detecting Interactions from Suspicious Sources
Rule: Monitor and flag interactions originating from:
Contracts with closed source code.
Addresses funded by Tornado Cash or other mixers.
Addresses identified as malicious by community threat intelligence or on-chain oracles.
Why It Matters: Interactions from such sources are often linked to exploit attempts. Attackers typically use mixers and anonymized contracts to obscure their tracks, making it crucial to flag these interactions for deeper investigation.
2. Tracking Transactions Involving Flash Loans
Rule: Detect and analyze transactions that involve flash loans.
Why It Matters: While not inherently malicious, flash loans are often used by attackers. Their use demands closer scrutiny to uncover potential threats hidden in complex transaction sequences.
3. Monitoring Abnormal Balance Fluctuations
Rule: Define thresholds for balance changes in both native assets and ERC20 tokens. Flag any transactions that result in abnormal or unexpected shifts.
Why It Matters: Sudden or significant changes in a contract’s balance often signal potential exploits, such as unauthorized withdrawals, minting bugs, or value-draining attacks. Real-time detection of these fluctuations enables faster remediation.
4. Identifying Interactions with Rarely Used Functions
Rule: Track calls to contract functions that are seldom invoked.
Why It Matters: Attackers frequently target obscure or rarely used functions that might have been overlooked during development or audits. Monitoring these interactions helps surface unusual activity and ensures these functions are not exploited unnoticed.
5. Detecting Spikes in Failed Transactions
Rule: Monitor the number of failed transactions interacting with the contract over a set time frame. Flag any spikes that exceed normal activity levels.
Why It Matters: A sudden increase in failed transactions can indicate deliberate DoS attacks, bugs in the contract, or malicious usage by attackers. Identifying these spikes early helps mitigate issues before they escalate.
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