[Firehol-support] Logging of DDoS attacks

Costa Tsaousis costa at tsaousis.gr
Sun Apr 3 22:56:47 BST 2005


Currently the "protection" statement can detect TCP and ICMP floods. I
think it would be relatively easy to have a global flood detector there.

In v1.231 (get it from http://firehol.sf.net/firehol.tar.gz) I have
written the protection 'all-floods'. To use it, put first just after any
interface or router statement.

protection all-floods <freq> <burst>

For <freq> and <burst> check the docs of 'protection'.

This one puts a threshold to all NEW connection requests (any protocol),
indepedently of whether there is a listening server or not. The overflow
requests are dropped, and of course there will be a log with "ALL FLOODS"
when this happens.

Note however, that a firewall may not be the "perfect" solution for this
problem. Maybe, you need an IDS (intrution detection system). Have you
check snort?



On Sat, April 2, 2005 1:15, Bernhard Gruen said:
> Hello Costa, hello list members,
> at the moment my server housing provider has some trouble with incoming
> DDoS attacks. Therefore some people on a private inofficial message board
> discussed about detection and logging of these kind of attacks.
> I stated that FireHOL has support for "accept with limit". With this
> option enabled I can log that my server is flooded on only one service.
> But I am not able to detect that my server is flooded with UDP packets on
> many fast changing ports. Someone else thought that he could use tcpdump
> to detect such a kind of attack but I am sure that this is not the best
> solution. I hope that IPtables/FireHOL is able to log such attacks too.
> Can someone give me a hint how to do this?
> Our goal is to write a tool that searches the logs for messages about
> possible DDoS attacks from IPtables/FireHOL.
> Many thanks for reading my message and many many thanks in advance for
> answering.
> Bernhard Gruen from Germany
> btw. FireHOL is beloved by many members of that private message board.
> Thank you for your piece of god-like software!
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