A reentrancy attack is a type of vulnerability that occurs when a contract calls an external contract that calls back into the original contract before the original contract has finished executing. This can allow the attacker to manipulate the contract's state and potentially steal funds.
To prevent reentrancy attacks, it's important to carefully consider the order in which external contracts are called and to use guards such as mutexes to ensure that the contract's state is not modified while it is in the process of executing.
Access control vulnerabilities occur when a contract does not properly enforce permissions, allowing unauthorized parties to access or modify sensitive data or functions. To prevent access control vulnerabilities, it's important to carefully design and implement a system for granting and revoking access to resources.
Arithmetic vulnerabilities occur when a contract performs arithmetic operations on untrusted input, which can lead to unexpected or incorrect results. To prevent arithmetic vulnerabilities, it's important to validate and sanitize input to ensure that it meets the required format and range, and to use robust libraries or functions for performing arithmetic operations.
Denial of Service (DoS) vulnerabilities occur when a contract can be deliberately strained or flooded with requests or transactions, causing it to become unresponsive or unavailable to other users. To prevent DoS vulnerabilities, it's important to design contracts to handle high volumes of requests and to implement rate limiting or other measures to prevent abuse.
Bad randomness vulnerabilities occur when a contract relies on weak or predictable sources of randomness, which can allow an attacker to predict or influence the outcome of certain actions. To prevent bad randomness vulnerabilities, it's important to use secure and reliable sources of randomness, such as hardware random number generators or block hashes.
Time manipulation vulnerabilities occur when a contract relies on the current time or block timestamp to make decisions, and an attacker is able to manipulate these values to their advantage. To prevent time manipulation vulnerabilities, it's important to use on-chain sources of time that are more difficult to manipulate, such as block timestamps or the latest block hash.