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Slowloris DoS Tool: It Can Bring Down Apache 1.x/2.x

Web server that use threaded processes such as Apache and others can be targeted using interesting HTTP DoS tool that has been released in wild. Tool can eat up all resources while it holds the connection open to server and keep sending incomplete HTTP requests. End result Apache run out of memory and comes under DoS attack.
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Lighttpd run php from different host using mod_proxy / mod_fastcgi

Lighttpd allows you to run php from different hosts. This is quite useful:

a] If you want to run php 4 locally and php 5 from remote host
b] Load balancing dynamic content
c] Added layer for security for chrooted jails etc

If you would like to run wikipedia / sf.net like site, you can use this technique. You can use mod_proxy or standard mod_fastcgi for this purpose.

How it works?

You need to use spawn-fcgi binary that spawns fastcgi processes. With spawn-fcgi you can bind php to particular port or unix-domain socket (little fast as compare to tcp port). It will take off some load from the webserver you have to control the FastCGI process by a external program like spawn-fcgi.

For example following command uses unix-domain to launch fastcgi process:
spawn-fcgi -s /tmp/php-fastcgi.sock -f /usr/bin/php-cgi -u lighttpd -g lighttpd -C 5 -P /var/run/spawn-fcgi.pid

This one bind itself to TCP port 8081
spawn-fcgi -p 8081 -a -f /usr/bin/php-cgi -u lighttpd -g lighttpd -C 5 -P /var/run/spawn-fcgi-1.pid


  • -f {fcgiapp} filename of the fcgi-application, e.g php - /usr/bin/php-cgi
  • -a {addr} : bind to ip address
  • -p {port} : bind to tcp-port
  • -s {path} : bind to unix-domain socket
  • -C {childs} : (PHP only) numbers of childs to spawn (default 5)
  • -P {path} : name of PID-file for spawed process, so that we can kill process later on
  • -n : no fork (for daemontools)
  • -c {dir} : chroot to directory
  • -u {user} : change to user-id
  • -g {group} : change to group-id

Using mod_proxy / mod_fastcgi, we can process everything on or cluster of php servers:

Web server <----> php-request <----> PHP listing on 

A php / ruby / java app cluster server:

Web server <----> php-request <----> // PHP listing on
                              // PHP listing on
                             // PHP listing on 

Task: Run php from and 8081 port

Make sure you copy spawn-fcgi file to, now enter following command:
# spawn-fcgi -p 8081 -a -f /usr/bin/php-cgi -u lighttpd -g lighttpd -C 10 -P /var/run/spawn-fcgi.pid
Make sure firewall is not blocking access to

Now open ligttpd.conf on other host and enter mod_fastcgi as config as follows:

fastcgi.server = ( ".php" =>
       "host" => "",
       "port" => 8081

Save and close the file. Restart lighttpd:
# /etc/init.d/lighttpd restart

You can use mod_proxy configuration as follows, if one of the hosts goes down the all requests for this one server are moved equally to the other servers.

$HTTP["host"] == "www.myweb2.0.com" {
  proxy.balance = "hash"
  proxy.server  = ( "" => ( ( "host" => "","port" => 8080  ),
                            ( "host" => "" ,"port" => 8080),
                            ( "host" => "" ,"port" => 8080),
                            ( "host" => "" ,"port" => 8080),
                            ( "host" => "" ,"port" => 8080) ) )

This is just an introduction, feel free to explore mod_proxy documentation for more information.