To hamess safe operation of Web-based systems in Web environments, we propose a Server-based SHA-1 Page-digest Algorithm (SSPA) to verify the integrity of Web contents before the server issues an HlTP-Response to a user request. In addition to standard security measures, our Java implementation of SSPA, which is called Dynamic Security Surveillance Agent (DSSA), provides further security in terms of content integrity to Web-based systems. Its function is to prevent display of altered Web contents, through malicious acts of attackers and intruders, on client machines. This is to protect the reputation of organisations from cyber attacks and to ensure safe operation of Web systems by dynamically monitoring the integrity of sites content on demand. We will discuss our jindings in terms of applicability and practicality of the proposed system. We also discuss its time metrics specifically in relation to its computational overhead at the Web server as well as the overall latency from the clients’ point of view, using different Intemt access methods. SSPA, DSSA, experimental results and related work are discussed. Para intentar reducir los ataques a los sitios web un grupo de profesionales desarrollo un agente verificador de contenido web “server-side” (Hace referencia a las operaciones que son llevadas a cabo por el servidor en una relacion clienteservidor en una red de computadoras como internet u otras redes. Su reciproco es client-side). Que de forma automatica y dinamica intercepta los procesos de la solicitud del usuario antes de que el servidor Web responda al cliente. Este sistema es diferente de los sistemas utilizados actualmente donde los clientes utilizan tecnologias como la firma digital o claves de cifrado, como parte de software de confianza del cliente, al realizar la verificacion de paginas solicitadas.