ddos on apache

packets · 09-14-2012, 11:41 AM

I notice that a bot is attacking my http. I see lots of GET request sometimes 20-30 request in just a seconds! How do I block or limit http request per ip? I'm using apache. I already added module mod_evasive but it seems it was not loaded though the DOSSystemCommand command under mod_evasive20.c Ifmodule.

Any suggestions?

YankeePride13 · 09-14-2012, 12:14 PM

You should talk to your ISP.

Noway2 · 09-14-2012, 12:36 PM

I agree that talking to your upstream service provider would be in order as the best place to block or filter the traffic would be before it even enters your system. Anything that you do will consume resources.

Aside from that, some things you can try locally:
1 - rate limit filtering in IPTables. This can be difficult because it requires you to balance the needs of valid traffic versus the malicious traffic.
2 - create a robots.txt, though if it is a malicious bot it is unlikely to abide by this
3 - investigate mod_dosevasive (found from seaching, don't know enough about it to endorse or not)
4 - investigate mod_security
5 - Depending on the requests, try fail2ban though it may be a little on the slow side
6 - look into using syn cookies.

Edit: to really get at the meat of the problem you will need to actually capture traffic data and then try to create a filter based upon it. This is a rather advanced topic.

unSpawn · 09-14-2012, 01:21 PM

...in addition here's two limiting rules:

Code:

# Per /24 block:
-A INPUT -m tcp -p tcp --syn -m multiport --dports 80,443 -m connlimit --connlimit-above 8 --connlimit-mask 24 -j REJECT --reject-with tcp-reset
# 2 packets p/s std, burst to 10 pps per IP address:
-A INPUT -m tcp -p tcp -m multiport --dports 80,443 -m hashlimit --hashlimit 2/s --hashlimit-burst 10 --hashlimit-mode srcip,dstport --hashlimit-htable-size 1024 --hashlimit-htable-max 2048 --hashlimit-name HTTP --hashlimit-htable-gcinterval 1000 --hashlimit-htable-expire 1000 -m state --state NEW -j ACCEPT

See '/sbin/iptables -m hashlimit --help' for more.

packets · 09-14-2012, 09:17 PM

Thanks for the response. I guess I'll try iptables.