Log analysis with the elk stack

Log Analysis with the ELK
Stack (Elasticsearch,
Logstash and Kibana)
Gary Smith, Pacific Northwest National Laboratory

A Little Context
! The Five Golden Principles of Security
! Know your system
! Principle of Least Privilege
! Defense in Depth
! Protection is key but detection is a must.
! Know your enemy.
2

In the Days of Chinook
! For most of Chinook's lifetime, the MSC used the "free"
version of Splunk to review the syslogs.
! Splunk Inc. has an interesting licensing model that's sort
of like an all-you-can-eat buffet where you pay by the
pound:
! The more you ingest, the more you pay.
! If you ingest < 500MB of logs a day, Splunk is "free".
! If you go over that limit too many times, Splunk will
continue to index your logs but you can't view them until
you pay them $$$ or you reinstall Splunk.
! Consequently, I was always fiddling with Syslog-NG's
rules to keep the cruft out and keep the daily log data <
500MB.
3

The Dawning of Cascade
! When the talk about what would later be known as
Cascade started ramping up, I started looking at a
replacement for Splunk because I knew that I would not
be able to keep under the 500MB limit with two
supercomputers in operation.
! The price for a commercial license for Splunk for the
amount of log data the MSC's systems produced would
be prohibitive.
4

Alternatives to Splunk
! I looked at a lot of alternatives to Splunk. These are just
some of them:
! Graylog2
! Nxlog
! Octopussy
! Logscape,
! ELSA
! LOGanalyzer
! Logalyzer
! Logwatcher
! logHound
! logReport
! Logsurfer
! PHP-Syslog-NG
5

Alternative to Splunk
! Some wouldn't build. Some wouldn’t work.
! Some were slow.
! Some had an abysmal user interface.
! Most all of them had a MySQL, PostgreSQL, or similar
relational database backend for storage and retrieval.
6

The Solution: ELK Stack [Elasticsearch,
Logstash, Kibana]
! Elasticsearch: Indexing, storage and retrieval engine
! Logstash: Log input slicer and dicer and output writer
! Kibana: Data displayer
7

Early Experiments With The Stack
! In the early stages of the ELK stack, the pieces didn't play
well together.
! Early versions of Logstash needed specific versions of
Elasticsearch and those weren't the latest ones.
! This caused some problems because Kibana wanted the
latest version of Elasticsearch.
! So I tried a couple of alternatives to ELK.
8

EFK
! EFK => Elasticsearch FluentD Kibana
! This worked pretty well.
! Good points:
! With FluentD, you install it, point it at Elasticsearch, point your
syslogs at Fluentd and you're good to go.
! Bad Points:
! There's not much you can do to extend FluentD to do things with
the syslog events coming in.
9

ERK
! ERK => Elasticsearch Rsyslogd Kibana
! There's an Rsyslogd plugin that takes syslog events and
sends them to Elasticsearch.
! Good points:
! Much like FluentD, you install it, point it at Elasticsearch and point
your syslogs at Rsyslogd and you're good to go.
! Bad Points:
! The plugin requires the very latest version of Rsyslogd, so you
have to build the latest version of Rsyslogd and the plugin.
! Then, you have to maintain the version of Rsyslogd and the plugin
since it's two major revisions above what's available in RHEL.
10

Finally, One Big Happy Family
! The dysfunctional aspects of the ELK stack got worked
out.
! Now the members of the ELK stack play well together
after being unified with help from the Elasticsearch
people.
11

Components of The ELK Stack
[Elasticsearch Logstash Kibana]
12

Logstash
! Logstash was developed by Jordan Sissel when he was a
system administrator at Dreamhost.
! Jordan needed something that could handle a peak of
20,000 messages per second.
! Logstash is easy to set up, scalable, and easy to extend.
13

Logstash Hosts
! In most cases there are two broad classes of Logstash
hosts:
! Hosts running the Logstash agent as an event forwarder that
sends you application, service, and host logs to a central
Logstash server.
! Central Logstash hosts running some combination of archiver,
indexer, search, storage, and web interface software which
receive, process, and store your logs.
14

Logstash Basic Configuration File
! A basic configuration file for Logstash has 3 sections:
! input
! filter
! output
15

The Input Section
16
! Inputs are the mechanism for passing log data to
Logstash. Some of the more useful, commonly-used ones
are:
! file: reads from a file on the filesystem, much like the UNIX
command "tail -f"
! syslog: listens on the well-known port 514 for syslog messages
and parses according to RFC3164 format
! lumberjack: processes events sent in the lumberjack protocol.
Now called logstash-forwarder.

The Filter Section
! Filters are workhorses for processing inputs in the Logstash
chain.
! They are often combined with conditionals in order to perform a
certain action on an event, if it matches particular criteria.
! Some useful filters:
! grok: parses arbitrary text and structures it.
! Grok is currently the best way in Logstash to parse unstructured
log data into something structured and queryable.
! With 120 patterns shipped built-in to Logstash, it’s more than
likely you’ll find one that meets your needs!
! mutate: The mutate filter allows you to do general mutations to fields.
You can rename, remove, replace, and modify fields in your events.
! drop: Drop an event completely, for example, debug events.
! geoip: Adds information about geographical location of IP addresses
(and displays amazing charts in Kibana)
17

The Output Section
18
! Outputs are the final phase of the Logstash pipeline.
! An event may pass through multiple outputs during
processing, but once all outputs are complete, the event
has finished its execution.
! Some commonly used outputs include:
! elasticsearch: If you’re planning to save your data in an efficient,
convenient and easily queryable format… Elasticsearch is the
way to go. Period. Yes, we’re biased :)
! file: writes event data to a file on disk.
! statsd: a service which "listens for statistics, like counters and
timers, sent over UDP and sends aggregates to one or more
pluggable backend services".
! If you’re already using statsd, this could be useful for you!

Elasticsearch: Hard made Easy
! Elasticsearch is a powerful indexing and search tool.
! The Elasticsearch team says, "Elasticsearch is a
response to the claim, 'Search is hard'".
! Elasticsearch is easy to set up, has search and index data
available RESTfully as JSON over HTTP and is easy to
scale and extend.
! It's released under the Apache 2.0 license and is built on
top of Apache's Lucene project.
19

Elasticsearch: How it works!
! Elasticsearch is a text indexing search engine.
! The best metaphor to describe Elasticsearch is the index
of a book.
! You flip to the back of a book, look up a word and then
find the reference page.
! This means that rather than searching text strings directly,
Elasticsearch creates an index from incoming text and
performs searches on the index rather than the content.
! As a result, it is very fast.
20

Elasticsearch Configuration
! Elasticsearch is started with a default cluster name of
"elasticsearch" and a random node name based on
characters from the X-Men.
! A new random node name is selected each time
Elasticsearch is restarted if one has not been chosen.
! If you want to customize your cluster and node names to
ensure unique names, edit /etc/elasticsearch/
elasticsearch.yml. !
! This is Elasticsearch's YAML-based configuration file.
21

The Kibana Web Interface
! The Kibana web interface is a customizable dashboard that
you can extend and modify to suit your environment.
! It allows the querying of events, creation of tables and graphs
as well as sophisticated visualizations.
! The Kibana web interface uses the Apache Lucene query
syntax to allow you to make queries.
! You can search any of the fields contained in a Logstash event,
for example, message, syslog_program, etc.
! You can use Boolean logic with AND, OR, NOT as well as
fuzzy searches and wildcard searches.
! You can:
! Build complex queries (including saving them and displaying the
results as a new panel)
! Graph and visualize data
! Produce tables and display data on maps and charts.
22

Troubleshooting: Is It Running?
! How do you tell if Elasticsearch is running? !
! Do this: curl http://10.0.0.1:9200/_status?pretty=true!
! This will return a page that contains a variety of
information about the state and status of your
Elasticsearch server.!
23

Troubleshooting: Are Logstash And
Elasticsearch Working Together?
! How can you check to see if Logstash is getting events to
Elasticsearch and they are getting indexed?
! Do this:
curl "http://localhost:9200/_search q=type:syslog&pretty=true" !
24

Troubleshooting: Syntax Checking Your
Logstash Configuration File
! After you've written/modified your Logstash configuration
file, how do you know it's syntactically correct before you
put it into production
! Do this:
/opt/logstash/bin/logstash agent -f logstash.conf --configtest !
25

Getting Rid Of Old Data
! One of the things I could never figure out with Splunk is
"How do I get expire old data out of Splunk?"
! What about Elasticsearch? Can I expire old data out of
Elasticsearch and keep only what's recent and relevant?
! As it turns out, like most things in the Linux-Sphere,
there's more than one way to do it.
! I have a daily cron job that runs a Perl script that deletes
data out of Elasticsearch older that 31 days.
! There is also a python program called Curator by Aaron
Mildenstein that helps you curate, or manage your
Elasticsearch indices like a museum curator manages the
exhibits and collections on display.
26

Debugging Grok Patterns
! Remember those patterns I was using in the grok filter to
parse out the fields in a syslog event? How did I come up
with those?
! I used the Grok Debugger at http://grokdebug.herokuapp.com/
to work out the construction of the pattern.
! The Grok Debugger is an interactive web page that
facilitates rapid creation of patterns based on sample
input.
27

The Grok Debugger In Action
28

References
! http://www.elastic.co/
! http://logstash.net/docs/latest
! https://www.elastic.co/products/kibana
! https://github.com/elastic/curator/wiki
! http://www.fluentd.org/
! http://www.rsyslog.com/
! http://grokdebug.herokuapp.com/
29

Questions?
30
Gary Smith
Information System Security Officer, Molecular Science
Computing, Pacific Northwest National Laboratory
Richland, WA
gary.smith@pnnl.gov

Log analysis with the elk stack

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