[Snort-users] Understanding MetaData

Joel Esler (jesler) jesler at ...589...
Sun Dec 6 13:54:30 EST 2015


In the FirePOWER product, service is detected, not reliant on port.  So, the "service" metadata is automatic in the product.

However, in open source Snort, you either have to use openappid to detect the services, or you have to specify them using a static file, called the Host Attributes table.  xml based, you're correct.



--
Joel Esler
Manager, Talos Group
Sent from my iPad

On Dec 6, 2015, at 1:50 PM, paul meding <medingtac at ...11827...<mailto:medingtac at ...11827...>> wrote:

Not snort answer per se but metadata is to bring context to network traffic.  Magic numbers can identify applications, filetypes, etc based upon the offsets that are used in their implementations.  in this way if someone renames for example a .zip file as a .abc to bypass filtering, metadata creation will still identify it as a .zip file due to the raw packets.  same way that if someone sends http traffic across a non http port ...it is still identified as http just over non standard port.  Snort can create and act off metadata as well as some other network free tools like netminer and RSA's investigator that you c an download and further see how metadata can make your analysis much more effective and make you a faster analyst.

meta can be used to identify filetypes, applications, geo, match domain malware lists, protocols, flags, payload statistics, so many things it would be impossible to list them all.  In snort it's used so even if traffic isnt on the typical port used by ssh for example, its still identified as such so it can't be fooled by our wonderful advanced adversaries we are looking to thwart.

Paul



On Sun, Dec 6, 2015 at 11:53 AM, Rafael Leiva-Ochoa <spawn at ...17369...<mailto:spawn at ...17369...>> wrote:
Any takers...


On Friday, December 4, 2015, Rafael Leiva-Ochoa <spawn at ...17369...<mailto:spawn at ...17369...>> wrote:
Hi All,

    I am trying to understand how "metadata: service http"  and other service types work.

I tried reading these documents:

http://manual.snort.org/node323.html

and

http://manual.snort.org/node22.html#targetbased

But, I am still a bit confused..: (

As I read, the document, it stated the following: "The service Metadata Key is only meaningful when a Host Attribute Table is provided".

The confusing part is a lot of Talos signatures us "metadata: service http", but there is no Host Attribute Tables created for that by default when I installed snort. How are those signatures going to work without it?

On the snort.conf there is no setting to tell snort to load the Attributes XML's. How is that done?

I also tried creating a custom rule on the local.rules file to better my understanding of "metadata service" using "ssh",  but it does not fire when I use it. It only works when I remove the "service ssh".

here is the rule:


alert tcp $HOME_NET any -> $HOME_NET 22 ( \

        msg:"SSH Brute Force Attempt"; \

        flow:established,to_server; \

        content:"SSH"; nocase; offset:0; depth:4; \

        detection_filter:track by_src, count 3, seconds 60; \

        sid:1000001; metadata:service ssh; rev:1;)

My understanding of metadata is that it is used to detect that someone is using a service not based on the port, but based on what the protocol is exhibiting. From example, if I ssh to a server using port 4598, which is not a standard ssh port, the "metadata service ssh" will be able to see it is ssh even though I had port 22 on the signature for the destination port.

Any input and answers would be great.

Thanks,

Rafael

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