I got hit with a mega-wave last night.. they kept consuming all my tcp/ip ports ( my current limit is 2048, double the linux default ).. i kept the site online for others only by restarting apache repeatedly. The blast lasted 15 minutes and it totally cut through my protection.
I'm not sure if i should tune linux' max TCP/IP ports and apache's max request workers into the stratosphere or leave it the way it is. I do have lots of available cpu/ram.
Something about how the bots work on the other end has the bots holding the TCP/IP port open for much longer than usual. It resembles a slow loris attack. I already have mitigations against that, but the number of simultaneous IPs is too high and too unique.
I'm not surprised if they cut right through cloudflare. I think the pool of residential proxies is enormous and rotates too often for something like cloudflare or some other algorithm to catch them.
Anubis is a good idea. It may result in a worsening of stuck tcp/ip ports. Same with a markov generator, etc.