Smart contracts on the Ethereum blockchain have revolutionized decentralized applications (dApps) but remain vulnerable to various security threats. In response, this paper introduces EthereumGuard, a pioneering Embedded Intrusion Detection System (EIDS) designed to bolster the security of smart contracts. By embedding intrusion detection mechanisms directly within contract code, EthereumGuard proactively monitors and identifies anomalous behavior, enabling swift responses to potential attacks. Leveraging blockchain transparency and deterministic execution, EthereumGuard offers robust protection against a spectrum of threats, including reentrancy and denial-of-service attacks.