"grep -i ssl /path/to/vrt/rules/files" would be a good start
$ grep -i ssl * | wc
131 2642 39057
I'm thinking of something like this
alert tcp $HOMW_NET 443 -> $EXTERNAL_NET any (msg:"NON SSL response"; \
flowbits:isnotset,sslv2.client_hello.request; \
flowbits:isnotset,sslv3.client_hello.request; \
flowbits:isnotset,tlsv1.client_hello.request; \
flow:established,to_client; sid:1000000; rev:1; )
This presumes that the client requesting data would not initiate with a
client hello so the response would not have client_hello set.
You might have to play with it a little but it should be possible.
Russell Fulton wrote:
Hellman, Matthew wrote:
Thanks for you reply Russell. SSL/TLS is epitome of the double edged
sword;-) I realize that the "bad guy" can wrap his traffic in an SSL
tunnel. If we cared enough to spend big $$, there are enterprise proxy
solutions that can inspect SSL (by performing a MITM). This is simply an
effort to raise the bar a little bit...I'm trying to catch the "stupid
guy" and the "stupid bad guy";-) There are plenty of them.
OK, I'm teaching my grandmother to suck eggs again :) It's one of the
problems with these mailing lists you never know how much knowledge to
poster has. Pleased to see you've taken it in good part :)
So to answer your real question, no I don't know of any sigs for this
but it should be doable without too much trouble. I'm guessing that you
may need to set a flowbit on the SYN packet and then use it to find the
first packet of the exchange which should have a recognisable format.
I've never tried to do this myself.
So, list: How does one write a set of rules that will look for
something in the first packet of a TCP session to a particular port?
Russell
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