Popular Customizations

This page outlines customizations and additions that are popular among Zeek users.

Note

This page lists externally-maintained Zeek packages. The Zeek team does not provide support or maintenance for these packages. If you find bugs or have feature requests, please reach out to the respective package maintainers directly.

You may also post in the Zeek Slack #packages channel or forum to get help from the broader Zeek community.

Log Enrichment

Community ID

Added in version 6.0.

Zeek includes native Community ID Flow Hashing support. This functionality has previously been provided through the zeek-community-id package.

Note

At this point, the external zeek-community-id package is still available to support Zeek deployments running older versions. However, the scripts provided by the package cause conflicts with those provided in Zeek 6.0 - do not load both.

Loading the policy/protocols/conn/community-id-logging.zeek and policy/frameworks/notice/community-id.zeek scripts adds an additional community_id field to the Conn::Info and Notice::Info record.

$ zeek -r ./traces/get.pcap protocols/conn/community-id-logging LogAscii::use_json=T
$ jq < conn.log
{
  "ts": 1362692526.869344,
  "uid": "CoqLmg1Ds5TE61szq1",
  "id.orig_h": "141.142.228.5",
  "id.orig_p": 59856,
  "id.resp_h": "192.150.187.43",
  "id.resp_p": 80,
  "proto": "tcp",
  ...
  "community_id": "1:yvyB8h+3dnggTZW0UEITWCst97w="
}

The Community ID Flow Hash of a conn_id instance can be computed with the community_id_v1 builtin function directly on the command-line or used in custom scripts.

$ zeek -e 'print community_id_v1([$orig_h=141.142.228.5, $orig_p=59856/tcp, $resp_h=192.150.187.43, $resp_p=80/tcp])'
1:yvyB8h+3dnggTZW0UEITWCst97w=

Address geolocation and AS lookups

Zeek supports IP address geolocation as well as AS (autonomous system) lookups. This requires two things:

Compilation of Zeek with the libmaxminddb library and development headers. If you’re using our Docker images or binary packages, there’s nothing to do: they ship with GeoIP support.

Installation of corresponding MaxMind database files on your system.

To check whether your Zeek supports geolocation, run zeek-config --have-geoip (available since Zeek 6.2) or simply try an address lookup. The following indicates that your Zeek lacks support:

$ zeek -e 'lookup_location(1.2.3.4)'
error in <command line>, line 1: Zeek was not configured for GeoIP support (lookup_location(1.2.3.4))

Read on for more details about building Zeek with GeoIP support, and how to configure access to the database files.

Building Zeek with libmaxminddb

If you build Zeek yourself, you need to install libmaxminddb prior to configuring your build.

RPM/RedHat-based Linux:
```
sudo yum install libmaxminddb-devel
```
DEB/Debian-based Linux:
```
sudo apt-get install libmaxminddb-dev
```
FreeBSD:
```
sudo pkg install libmaxminddb
```
Mac OS X:

You need to install from your preferred package management system (e.g. Homebrew, MacPorts, or Fink). For Homebrew, the name of the package that you need is libmaxminddb.

The configure script’s output indicates whether it successfully located libmaxminddb. If your system’s MaxMind library resides in a non-standard path, you may need to specify it via ./configure --with-geoip=<path>.

Installing and configuring GeoIP databases

MaxMind’s databases ship as individual files that you can download from their website after signing up for an account. Some Linux distributions also offer free databases in their package managers.

There are three types of databases: city-level geolocation, country-level geolocation, and mapping of IP addresses to autonomous systems (AS number and organization). Download these and decide on a place to put them on your file system. If you use automated tooling or system packages for the installation, that path may be chosen for you, such as /usr/share/GeoIP.

Zeek provides three ways to configure access to the databases:

Specifying the path and filenames via script variables. Use the mmdb_dir variable, unset by default, to point to the directory containing the database(s). By default Zeek looks for databases called GeoLite2-City.mmdb, GeoLite2-Country.mmdb, and GeoLite2-ASN.mmdb. Starting with Zeek 6.2 you can adjust these names by redefining the mmdb_city_db, mmdb_country_db, and mmdb_asn_db variables.
Relying on Zeek’s pre-configured search paths and filenames. The mmdb_dir_fallbacks variable contains default search paths that Zeek will try in turn when mmdb_dir is not set. Prior to Zeek 6.2 these paths were hardcoded; they’re now redefinable. For geolocation, Zeek first attempts the city-level databases due to their greater precision, and falls back to the city-level one. You can adjust the database filenames via mmdb_city_db and related variables, as covered above.
Opening databases explicitly via scripting. The mmdb_open_location_db and mmdb_open_asn_db functions take full paths to database files. Zeek only ever uses one geolocation and one ASN database, and these loads override any databases previously loaded. These loads can occur at any point.

Querying the databases

Two built-in functions provide GeoIP functionality:

function lookup_location(a:addr): geo_location
function lookup_autonomous_system(a:addr): geo_autonomous_system

lookup_location returns a geo_location record with country/region/etc fields, while lookup_autonomous_system returns a geo_autonomous_system record indicating the AS number and organization. Depending on the queried IP address some fields may be uninitialized, so you should guard access with an a?$b existence test.

Zeek tests the database files for staleness. If it detects that a database has been updated, it will automatically reload it. Zeek does not automatically add GeoIP intelligence to its logs, but several add-on scripts and packages provide such functionality. These include:

The notice framework lets you configure notice types that you’d like to augment with location information. See Notice::lookup_location_types and Notice::ACTION_ADD_GEODATA for details.
The policy/protocols/smtp/detect-suspicious-orig.zeek and policy/protocols/ssh/geo-data.zeek policy scripts.
Several Zeek packages.

Testing

Before using the GeoIP functionality it is a good idea to verify that everything is setup correctly. You can quickly check if the GeoIP functionality works by running commands like these:

zeek -e "print lookup_location(8.8.8.8);"

If you see an error message similar to “Failed to open GeoIP location database”, then your database configuration is broken. You may need to rename or move your GeoIP database files.

Example

The following shows every FTP connection from hosts in Ohio, US:

event ftp_reply(c: connection, code: count, msg: string, cont_resp: bool)
{
  local client = c$id$orig_h;
  local loc = lookup_location(client);

  if (loc?$region && loc$region == "OH" && loc?$country_code && loc$country_code == "US")
  {
    local city = loc?$city ? loc$city : "<unknown>";

    print fmt("FTP Connection from:%s (%s,%s,%s)", client, city,
      loc$region, loc$country_code);
  }
}

Log Writers

Kafka

For exporting logs to Apache Kafka in a streaming fashion, the externally-maintained zeek-kafka package is a popular choice and easy to configure. It relies on librdkafka.

redef Log::default_writer = Log::WRITER_KAFKAWRITER;

redef Kafka::kafka_conf += {
    ["metadata.broker.list"] = "192.168.0.1:9092"
};

Logging

JSON Streaming Logs

The externally-maintained json-streaming-logs package tailors Zeek for use with log shippers like Filebeat or fluentd. It configures additional log files prefixed with json_streaming_, adds _path and _write_ts fields to log records and configures log rotation appropriately.

If you do not use a logging archive and want to stream all logs away from the system where Zeek is running without leveraging Kafka, this package helps you with that.

Long Connections

Zeek logs connection entries into the conn.log only upon termination or due to expiration of inactivity timeouts. Depending on the protocol and chosen timeout values this can significantly delay the appearance of a log entry for a given connection. The delay may be up to an hour for lingering SSH connections or connections where the final FIN or RST packets were missed.

The zeek-long-connections package alleviates this by creating a conn_long.log log with the same format as conn.log, but containing entries for connections that have been existing for configurable intervals. By default, the first entry for a connection is logged after 10mins. Depending on the environment, this can be lowered as even a 10 minute delay may be significant for detection purposes in streaming setup.

Profiling and Debugging

jemalloc profiling

For investigation of memory leaks or state-growth issues within Zeek, jemalloc’s profiling is invaluable. A package providing a bit support for configuring jemalloc’s profiling facilities is zeek-jemalloc-profiling.

Some general information about memory profiling exists in the Troubleshooting section.