6.33. Datasets

Using the dataset and datarep keyword it is possible to match on large amounts of data against any sticky buffer.

For example, to match against a DNs black list called dns-bl:

dns.query; dataset:isset,dns-bl;

These keywords are aware of transforms. So to look up a DNS query against a MD5 black list:

dns.query; to_md5; dataset:isset,dns-bl;

6.33.1. Global config (optional)

Datasets can optionally be defined in the main config. Sets can also be declared from the rule syntax.

Example of sets for tracking unique values:

datasets:
  ua-seen:
    type: string
    state: ua-seen.lst
  dns-sha256-seen:
    type: sha256
    state: dns-sha256-seen.lst

Rules to go with the above:

alert dns any any -> any any (msg:”dns list test”; dns.query; to_sha256; dataset:isset,dns-sha256-seen; sid:123; rev:1;)
alert http any any -> any any (msg: “http user-agent test”; http.user_agent; dataset:set,ua-seen; sid:234; rev:1;)

It is also possible to optionally define global default memcap and hashsize.

Example:

datasets:
  defaults:
    memcap: 100mb
    hashsize: 2048
  ua-seen:
    type: string
    load: ua-seen.lst

or define memcap and hashsize per dataset.

Example:

datasets:
  ua-seen:
    type: string
    load: ua-seen.lst
    memcap: 10mb
    hashsize: 1024

6.33.2. Rule keywords

6.33.2.1. dataset

Datasets are binary: something is in the set or it’s not.

Syntax:

dataset:<cmd>,<name>,<options>;

dataset:<set|isset|isnotset>,<name> \
    [, type <string|md5|sha256>, save <file name>, load <file name>, state <file name>, memcap <size>, hashsize <size>];
type <type>
the data type: string, md5, sha256
load <file name>
file name for load the data when Suricata starts up
state
sets file name for loading and saving a dataset
save <file name>
advanced option to set the file name for saving the in-memory data when Suricata exits.
memcap <size>
maximum memory limit for the respective dataset
hashsize <size>
allowed size of the hash for the respective dataset

Note

‘load’ and ‘state’ or ‘save’ and ‘state’ cannot be mixed.

6.33.2.2. datarep

Data Reputation allows matching data against a reputation list.

Syntax:

datarep:<name>,<operator>,<value>, \
    [, load <file name>, type <string|md5|sha256>, memcap <size>, hashsize <size>];

Example rules could look like:

alert dns any any -> any any (dns.query; to_md5; datarep:dns_md5, >, 200, load dns_md5.rep, type md5, memcap 100mb, hashsize 2048; sid:1;)
alert dns any any -> any any (dns.query; to_sha256; datarep:dns_sha256, >, 200, load dns_sha256.rep, type sha256; sid:2;)
alert dns any any -> any any (dns.query; datarep:dns_string, >, 200, load dns_string.rep, type string; sid:3;)

In these examples the DNS query string is checked against three different reputation lists. A MD5 list, a SHA256 list, and a raw string (buffer) list. The rules will only match if the data is in the list and the reputation value is higher than 200.

6.33.3. Rule Reloads

Sets that are defined in the yaml, or sets that only use state or save, are considered dynamic sets. These are not reloaded during rule reloads.

Sets that are defined in rules using only load are considered static tests. These are not expected to change during runtime. During rule reloads these are reloaded from disk. This reload is effective when the complete rule reload process is complete.

6.33.4. Unix Socket

6.33.4.1. dataset-add

Unix Socket command to add data to a set. On success, the addition becomes active instantly.

Syntax:

dataset-add <set name> <set type> <data>
set name
Name of an already defined dataset
type
Data type: string, md5, sha256
data
Data to add in serialized form (base64 for string, hex notation for md5/sha256)

Example adding ‘google.com’ to set ‘myset’:

dataset-add myset string Z29vZ2xlLmNvbQ==

6.33.4.2. dataset-remove

Unix Socket command to remove data from a set. On success, the removal becomes active instantly.

Syntax:

dataset-remove <set name> <set type> <data>
set name
Name of an already defined dataset
type
Data type: string, md5, sha256
data
Data to remove in serialized form (base64 for string, hex notation for md5/sha256)

6.33.5. File formats

Datasets use a simple CSV format where data is per line in the file.

6.33.5.1. data types

string
in the file as base64 encoded string
md5
in the file as hex encoded string
sha256
in the file as hex encoded string

6.33.5.2. dataset

Datasets have a simple structure, where there is one piece of data per line in the file.

Syntax:

<data>

e.g. for ua-seen with type string:

TW96aWxsYS80LjAgKGNvbXBhdGlibGU7ICk=

which when piped to base64 -d reveals its value:

Mozilla/4.0 (compatible; )

6.33.5.3. datarep

The datarep format follows the dataset, expect that there are 1 more CSV field:

Syntax:

<data>,<value>