DDoS protection module suggestion

[Weibin Yao]

malte at 2010-11-3 10:19 wrote:
> I've recently been hit pretty hard with a nasty DDoS attack on a site of
> mine.
>
> With http://wiki.nginx.org/HttpLimitReqModule and
> http://wiki.nginx.org/HttpLimitZoneModule I was able to mitigate the
> attack reasonably well, but neither of these modules do what I'd really
> like to have done - temporarily serve only a plain 4xx or 5xx error
> message to any IP that is exhibiting clearly abusive behavior, like
> requesting the exact same page over and over again, or attempting to
> make a large amount of parallel connections (100+) at once. 
limit module can also limit the concurrent request uri.

http {
 
  limit_zone   one  $part_of_uri  10m;
 
  server {
    location /download/ {
      set $part_of_uri "download";
      limit_conn   one  100;
    }
  }
}

I have not tested it yet, you can have a try.

> This should
> be in effect for a configurable amount of time, but just 10 minutes or
> so would have worked well against my recent attack, as each attacking
> bot only tends to attack for a few minutes before its replaced by
> another bot.
>
> So my suggestion is either adding functionality to the Limit modules, or
> adding a new DDoS module which would use a set amount of memory to keep
> tab of all IPs that have requested anything in the past 10-15 seconds,
> and can mitigate DDoS attacks by analyzing recent request and connect
> patterns by IP.
> Posted at Nginx Forum: http://forum.nginx.org/read.php?2,147105,147105#msg-147105
>
>
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>   


-- 
Weibin Yao