IPsec (Internet Protocol Security) is a suite of protocols designed to secure communications across IP networks by authenticating and encrypting each IP packet of a communication session. It operates at the network layer (IP layer) and is widely used to establish secure connections over public networks, such as the Internet, most commonly in Virtual Private Networks (VPNs).
IPsec encrypts data packets, ensuring that sensitive information remains confidential as it travels over potentially insecure networks. It authenticates the source of data, verifying that packets come from a trusted sender and have not been tampered with. IPsec checks that data has not been altered in transit, protecting against tampering and replay attacks. IPsec assigns sequence numbers to packets to detect and prevent replay attacks, where a malicious actor intercepts and retransmits data.