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Re: Snort Anomaly
From: Doug Burks <doug.burks () gmail com>
Date: Thu, 9 Jan 2014 07:21:24 -0500

Hi Mr Smith,

Kevin provided some great recommendations and you can have many of
them up and running in about 15 minutes with Security Onion:
http://www.securityonion.net/

Security Onion gives you the following:
- Snort and Bro (with PF_RING)
- ELSA
- Full packet capture
- OSSEC HIDS
(and much more!)

We released an update yesterday that especially helps in finding the
anomalies in your network:
http://blog.securityonion.net/2014/01/new-securityonion-web-page-package.html

Hope that helps!

On Wed, Jan 8, 2014 at 11:00 AM, Kevin Ross <kevross33 () googlemail com> wrote:
It depends what you mean by anomaly. These days "anomaly" to me means odd
HTTP communications, useragents, geolocation patterns, traffic anomalies
like bad fields for DNS or hosts talking on protocols they shouldn't be like
non-DNS servers trying to contact external DNS etc. To be more capable of
detecting these things and other anomalies I suggest taking a network
security monitoring approach with multiple levels of tools. This means
collecting various data from IDS, network etc and applying detection to it.
An excellent recently released book on this is this which while I am not too
far into it the book is truly excellent; especially as it covers snort,
anomaly detection, BRO (which very nicely complements things like Snort).

http://www.amazon.co.uk/Applied-Network-Security-Monitoring-Collection/dp/0124172083/ref=sr_1_1?ie=UTF8&qid=1389194990&sr=8-1&keywords=applied+network+security+monitoring

Obviously though you don't need a book to learn this as you can read
documentation on each of these bits. To get to a good detection level I
would suggest looking into the following things:
- Make sure you have Snort tuned so you aren't overwhelmed and the rules and
preprocessors are setup as you want them. Read the Snort documentation on
this, a lot of rules and preprocessor settings will highlight traffic
anomalies anyway.

- Install BRO http://www.bro.org/. It can detect other anomalies and also
generates very detailed logs on HTTP traffic, file hashes, tunnels, DNS,
other protocols that will complement any alerts you get from Snort etc. I
then feed those logs and IDS logs and things into ELSA
http://code.google.com/p/enterprise-log-search-and-archive/ which allows me
to do querying on all events surrounding a snort alert and also a lot of
hunting (i.e show me all unique useragents in my traffic and it will count
them up and display that, show me all executables from certain countries
etc). With snort I also have Snorby setup and full packet capture with
openfpc so it can be queried easily from Snorby from alerts. It can also
extract files from the network (which Snort 2.9.6 can do too) but the
advantage is also hashing of all files in protocols. So executables, HTML
pages, Java files, PDFs everything is getting hashed so even if you don't
have a file you can search for the hashes on things like Virustotal.

- Setup full packet capture solution like OpenFPC, Moloch or StreamDB (I use
OpenFPC due to it being integrated into Snorby and it is less intense than
say Moloch which indexes network traffic for my sensors). This allows you to
analyse the traffic in depth depending how far you can go back (1 day min 3
days ideal but you may find it is only hours. Still some FPC for as long as
your disk space allows (and you can ignore hosts, protocols etc with BPF
filters to increase that time) is better than none.

- Other types of anomaly detection can be implemented in other things such
as if you have a SIEM with your firewall logs going into it if you create a
correlation rule for high port numbers (above 1024 but not well known high
port numbers like SIP ports etc) and then log for UDP and TCP firewall
denies for so many in a certain time like a minute period you will actually
pick out P2P protocols with no knowedge of the protocol itself. I.e Using
this logic and some negation for my enviroment I reliably have detected
(although it may not have been the only alert) BitTorrent Traffic, Zeus
trojan P2P protocol and other protocols for malware etc. This will be very
useful as P2P is used increasingly in malware families.

- Another good thing is PassiveDNS ideas which you can get going with
https://github.com/gamelinux/passivedns. Just logging in with NXDOMAINs into
a database with the web interface is good and for instance you can create a
lookup in Snorby so that when you have an IDS alert you can quickly lookup
the IP in your PassiveDNS database for domains which can very quickly help
you determine a false positive or a true positive and even when the incident
first appeared. I.e I have had alerts for exploit kits but through DNS for
the other names resolved to the IP I have found previously used domains and
when they were seen and am then able to look back and other logs at those
times. Also using regular expressions, blacklists and other methods in SIEM
for NXDOMAINs for instance I can detect malicious or suspect domains: i.e
alerts for domain generation algorithm domains
(https://blog.damballa.com/archives/1504), bad domains, supect domains such
as each day I extract with a script all new domains queried (and also cases
where new IPs mapped to a name) that day and then with some negation and
other things. The logic being if that is the first time ever it has appeared
within your enterprise and it looks kind of suspicious it just might be.

While no one thing here is a silver bullet the combination of all the
combined tools and methods is basically provided lots of ability to detect
intrusions, properly analyse them, hunt for the unknown, detect anomalies
etc. With this you will end up with:

- Snort alerting you to all kinds of intrusions and anomalies. For anomalies
though protocol rules and the preprocessors which you can read about in the
documentation is where you should look.
- BRO IDS providing detailed logging and if fed into something like ELSA,
SPLUNK, Logstash etc analytics. Also actual on disk BRO logs compress to
very little space automatically so essentially you have a historical record
of all flows, IRC chats, FTP traffic, HTTP records, file hashes and so on
for a long time of perhaps many months or even years.
- Full packet capture. Useful for short term but high detail analysis
- File extraction for analysis if you implement in BRO/Snort. You can then
do other analysis like running tools on them, checking the file hashes on
Virustotal frmo BRO etc
- PassiveDNS will allow you to analyse URLs and IPs for their relationships
and it will provide a long term historical analysis (i.e a partner
organsiation says they have malware which talks to badguys.com. Have you
been hit? You can go to that, type it in and if you get results you will
have a first and last time to begin hunting through other logs and BRO would
have even more detail. Also with regex you can detect all kind of anomalies
and if you look at research like  http://labs.umbrella.com/
http://www.lastline.com/papers/dns.pdf and
https://www.damballa.com/damballa-labs/publications.php you might get more
ideas on things in DNS to look for to detect malicious activity (or simply
feeding in blacklists of known bad ones).

Hope that helps,
Kevin


On 7 January 2014 18:38, Mr Smith <engineer.demo2020 () gmail com> wrote:

Hi
I Have a question about Snort:
What is the best solution to improve Snort performance in terms of
"Anomaly Detection" Capability?
What is the best solution to add "Anomaly Detection" capability into
Snort?
1. Using a Host-Based IDS(like what?) in conjunction with Snort(NIDS)?
2. Adding anomaly based plugins(like what) into Snort?
3....?

Thanks


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Rapidly troubleshoot problems before they affect your business. Most IT
organizations don't have a clear picture of how application performance
affects their revenue. With AppDynamics, you get 100% visibility into your
Java,.NET, & PHP application. Start your 15-day FREE TRIAL of AppDynamics
Pro!
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-- 
Doug Burks

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