No hay herramientas integradas para evitar el DoS. Si está escribiendo Google Apps usando java, puede usar el filtro service.FloodFilter. La siguiente pieza de código se ejecutará antes que cualquiera de sus Servlets.
package service;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
/**
*
* This filter can protect web server from simple DoS attacks
* via request flooding.
*
* It can limit a number of simultaneously processing requests
* from one ip and requests to one page.
*
* To use filter add this lines to your web.xml file in a <web-app> section.
*
<filter>
<filter-name>FloodFilter</filter-name>
<filter-class>service.FloodFilter</filter-class>
<init-param>
<param-name>maxPageRequests</param-name>
<param-value>50</param-value>
</init-param>
<init-param>
<param-name>maxClientRequests</param-name>
<param-value>5</param-value>
</init-param>
<init-param>
<param-name>busyPage</param-name>
<param-value>/busy.html</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>JSP flood filter</filter-name>
<url-pattern>*.jsp</url-pattern>
</filter-mapping>
*
* PARAMETERS
*
* maxPageRequests: limits simultaneous requests to every page
* maxClientRequests: limits simultaneous requests from one client (ip)
* busyPage: busy page to send to client if the limit is exceeded
* this page MUST NOT be intercepted by this filter
*
*/
public class FloodFilter implements Filter
{
private Map <String, Integer> pageRequests;
private Map <String, Integer> clientRequests;
private ServletContext context;
private int maxPageRequests = 50;
private int maxClientRequests = 10;
private String busyPage = "/busy.html";
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException
{
String page = null;
String ip = null;
try {
if (request instanceof HttpServletRequest) {
// obtaining client ip and page URI without parameters & jsessionid
HttpServletRequest req = (HttpServletRequest) request;
page = req.getRequestURI();
if (page.indexOf(';') >= 0)
page = page.substring(0, page.indexOf(';'));
ip = req.getRemoteAddr();
// trying & registering request
if (!tryRequest(page, ip)) {
// too many requests in process (from one client or for this page)
context.log("Flood denied from "+ip+" on page "+page);
page = null;
// forwarding to busy page
context.getRequestDispatcher(busyPage).forward(request, response);
return;
}
}
// requesting next filter or servlet
chain.doFilter(request, response);
} finally {
if (page != null)
// unregistering the request
releaseRequest(page, ip);
}
}
private synchronized boolean tryRequest(String page, String ip)
{
// checking page requests
Integer pNum = pageRequests.get(page);
if (pNum == null)
pNum = 1;
else {
if (pNum > maxPageRequests)
return false;
pNum = pNum + 1;
}
// checking client requests
Integer cNum = clientRequests.get(ip);
if (cNum == null)
cNum = 1;
else {
if (cNum > maxClientRequests)
return false;
cNum = cNum + 1;
}
pageRequests.put(page, pNum);
clientRequests.put(ip, cNum);
return true;
}
private synchronized void releaseRequest(String page, String ip)
{
// removing page request
Integer pNum = pageRequests.get(page);
if (pNum == null) return;
if (pNum <= 1)
pageRequests.remove(page);
else
pageRequests.put(page, pNum-1);
// removing client request
Integer cNum = clientRequests.get(ip);
if (cNum == null) return;
if (cNum <= 1)
clientRequests.remove(ip);
else
clientRequests.put(ip, cNum-1);
}
public synchronized void init(FilterConfig config) throws ServletException
{
// configuring filter
this.context = config.getServletContext();
pageRequests = new HashMap <String,Integer>();
clientRequests = new HashMap <String,Integer>();
String s = config.getInitParameter("maxPageRequests");
if (s != null)
maxPageRequests = Integer.parseInt(s);
s = config.getInitParameter("maxClientRequests");
if (s != null)
maxClientRequests = Integer.parseInt(s);
s = config.getInitParameter("busyPage");
if (s != null)
busyPage = s;
}
public synchronized void destroy()
{
pageRequests.clear();
clientRequests.clear();
}
}
Si está utilizando Python, entonces puede que tenga que rodar su propio filtro.
Probablemente voy a usar Java para la velocidad extra, por lo que esto podría ayudar. – Zifre
App Engine cuenta con soporte para filtro DoS desde hace un tiempo. –
El filtro DOS solo funciona para IP conocida ¿verdad? No puede tratar con ataques DDOS que IP no se conocen antes de que comience el ataque. Además, el ejemplo anterior no puede proteger el uso del ancho de banda de los recursos estáticos –