[Snort-users] tcp syn flood attack

Russ Combs rcombs at ...1935...
Mon Jun 14 16:55:05 EDT 2010


Maybe someone else can help you with snortsam, but for sure you need to
change:

15 minutes , timeout <T>

to

timeout 900,

On Mon, Jun 14, 2010 at 4:48 PM, Luis Daniel Lucio Quiroz <
luis.daniel.lucio at ...11827...> wrote:

> thanx
> well what i'm trying is to use rate_filter with snortsam.  I've ported
> sucessfully snortsam to use with snortsam to plush fw rules
>
> > rate_filter \
> >     gen_id 135, sig_id 1, \
> >     track by_dst, \
> >     count 10, seconds 60, \
> >     new_action fwsam: src[IN], 15 minutes , timeout <T>, \
> >     apply_to 10.1.1.100
>
> i wonder if this could work
>
>
>
> Le lundi 14 juin 2010 15:15:30, Russ Combs a écrit :
> > That rule won't exactly catch a syn flood.  Assuming the rule fires the
> way
> > you want without the detection_filter, it will, with the
> detection_filter,
> > fire when more than 10 such *packets* are received in 60 seconds.
> >
> > If you truly want a syn flood detection, you need a rate_filter something
> > like this:
> >
> > rate_filter \
> >     gen_id 135, sig_id 1, \
> >     track by_dst, \
> >     count 10, seconds 60, \
> >     new_action drop, timeout <T>, \
> >     apply_to 10.1.1.100
> >
> > where <T> is the duration you want to drop before allowing the traffic
> > through again.
> >
> > That will catch an excessive rate of syns.
> >
> > Note that this rate filter applies to the destination IP.  You can also
> > write a separate rule and then rate filter that rule.
> >
> > Russ
> >
> > On Mon, Jun 14, 2010 at 3:48 PM, Luis Daniel Lucio Quiroz <
> >
> > luis.daniel.lucio at ...11827...> wrote:
> > > Ok, after reading ineed to drop a highg  tcp syn flood, to my squid
> > >
> > > is this rule  fine or shall do other tunning
> > >
> > >
> > > drop tcp any any > 10.1.1.100 3128 ( \
> > >
> > >    msg:”Squid sync flood”;
> > >    flow:established,to_server; \
> > >    detection_filter: track by_src, count 10, seconds 60; \
> > >    sid:1000001; rev:1;)
> > >
> > > Reegards,
> > >
> > > LD
> > >
> > > Le lundi 14 juin 2010 11:58:54, Russ Combs a écrit :
> > > > That is documented in the Snort manual and in README.filters in the
> > > > tarball.
> > > >
> > > > On Mon, Jun 14, 2010 at 12:43 PM, Luis Daniel Lucio Quiroz <
> > > >
> > > > luis.daniel.lucio at ...11827...> wrote:
> > > > > in 2.8 how is this rule?
> > > > >
> > > > > Le lundi 14 juin 2010 10:51:44, Russ Combs a écrit :
> > > > > > Snort 2.4 is out of date.  The latest Snort includes a rate-based
> > > > > > attack detection capability that addresses syn floods.  Have you
> > >
> > > tried
> > >
> > > > > downloading
> > > > >
> > > > > > the tarball from snort.org and building an inline version?
> > > > > >
> > > > > > Russ
> > > > > >
> > > > > > On Sun, Jun 13, 2010 at 6:42 PM, black_angel black_angel <
> > > > > >
> > > > > > black.sad.angel at ...11827...> wrote:
> > > > > > > Hello everybody
> > > > > > > my snort inline 2.4 can't detect a syn flood attack using
> hping3
> > > > > > > if someone can help me please to write a rule to avoid this
> > > > > > > attack tnx
> > >
> > >
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>
> Thanx Russ
>
>
>
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