Rules Syntax

group

Groups categorize alerts. They allow filtering related alerts in the Wazuh dashboard.

The default Wazuh ruleset already includes rules that use groups like syscheck,, attack,, and syslog,. As an example, you can filter alerts for these categories by querying rule.groups: attack or rule.groups: (syscheck OR syslog) in the Wazuh dashboard.

Every rule must belong to at least one group. To specify one or more groups for a rule, enclose the rule definition with the <group name="GROUP1_NAME,GROUP2_NAME,"> element. For example:

<group name="limits,">
 <rule id="100234" level="3">
    <if_sid>230</if_sid>
    <field name="alert_type">normal</field>
    <description>The file limit set for this agent is $(file_limit). Now, $(file_count) files are being monitored.</description>
  </rule>
</group>

You can also specify additional groups by including the <group> element within the rule definition. For example:

<group name="limits,">
  <rule id="100234" level="3">
    <if_sid>230</if_sid>
    <field name="alert_type">normal</field>
    <description>The file limit set for this agent is $(file_limit). Now, $(file_count) files are being monitored.</description>
   <group>syscheck,fim_db_state,</group>
 </rule>
</group>

To define rules that trigger only if another rule in a specific group has triggered, check the if_group and if_matched_group options.

rule

<rule> is the label that starts the block defining a rule. In this section, we describe the various options associated with this label.

Example:

<rule id="3151" level="10" frequency="8" timeframe="120">
  <if_matched_sid>3102</if_matched_sid>
  <same_source_ip />
  <description>sendmail: Sender domain has bogus MX record. </description>
  <description>It should not be sending email.</description>
  <mitre>
    <id>T1114</id>
    <id>T1499</id>
  </mitre>
  <group>multiple_spam,pci_dss_11.4,gdpr_IV_35.7.d,nist_800_53_SI.4,tsc_CC6.1,tsc_CC6.8,tsc_CC7.2,tsc_CC7.3,</group>
</rule>

The rule is created with ID: 3151 and it will trigger a level 10 alert if the rule 3102 has matched 8 times in the last 120 seconds.

match

Used as a requisite to trigger a rule. It will search for a match in the log event.

Example:

<rule id="100001" maxsize="300" level="3">
  <if_sid>100200</if_sid>
  <match>Queue flood!</match>
  <description>Flooded events queue.</description>
</rule>

If the rule 100200 is matched and the log message contains the phrase Queue flood!, the rule 100001 triggers a level 3 alert.

The attributes below are optional.

If match label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

regex

Used as a requisite to trigger a rule. It will search for a match in the log event.

Example:

<rule id="100001" level="3">
  <if_sid>100500</if_sid>
  <regex>\b(?:\d{1,3}\.){3}\d{1,3}\b</regex>
  <description>Matches any valid IP</description>
</rule>

If the rule 100500 is matched and the event contains any valid IPv4, the rule 100001 is triggered, generating a level 3 alert.

The attributes below are optional.

If regex label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

decoded_as

Used as a requisite to trigger a rule. It will be triggered if the event has been decoded by a certain decoder. Useful to group rules and have child rules inherit from it.

Example:

<rule id="53500" level="0">
  <decoded_as>smtpd</decoded_as>
  <description>OpenSMTPd grouping.</description>
</rule>

The rule will be triggered if the event was decoded by the smtpd decoder. You can create more rules specifically tailored for OpenSMTPd events that will inherit from this one.

category

Used as a requisite to trigger a rule. It will be triggered if the decoder includes the log in the specified category.

Example:

<rule id="1" level="0" noalert="1">
  <category>syslog</category>
  <description>Generic template for all syslog rules.</description>
</rule>

The rule will trigger if the log message has previously been decoded by the syslog decoder. However, since the level is set to 0, the event will not be displayed on the dashboard. Instead, it will be matched by other rules that might trigger alerts if needed.

field

Used as a requisite to trigger a rule. It will check for a match in the content of a field extracted by the decoder.

Below is the list of attributes.

Example:

<rule id="87100" level="0">
    <decoded_as>json</decoded_as>
    <field name="integration">virustotal</field>
    <description>VirusTotal integration messages.</description>
    <options>no_full_log</options>
</rule>

This rule groups events decoded from json that belong to an integration called VirusTotal. It checks the field decoded as integration and if its content is virustotal, the rule is triggered.

srcip

Used as a requisite to trigger a rule. It compares any IP address or CIDR block to an IP decoded as srcip.

Example:

<rule id="100105" level="8">
    <if_sid>100100</if_sid>
    <srcip>10.25.23.12</srcip>
    <description>Forbidden srcip has been detected.</description>
</rule>

This rule will trigger when that exact scrip has been decoded.

The attributes below are optional.

If srcip label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

dstip

Used as a requisite to trigger a rule. It compares any IP address or CIDR block to an IP decoded as dstip.

Example:

<rule id="100110" level="5">
    <if_sid>100100</if_sid>
    <dstip negate=”yes”>198.168.41.30</dstip>
    <description>A different dstip has been detected.</description>
</rule>

This rule will trigger when a dstip different from 198.168.41.30 is detected.

The attributes below are optional.

If the dstip label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

srcport

Used as a requisite to trigger a rule. It will check the source port (decoded as srcport).

Example:

<rule id="100110" level="5">
    <if_sid>100100</if_sid>
    <srcport type="pcre2">^5000[0-7]$</srcport>
    <description>Source port $(srcport) is detected.</description>
</rule>

This rule will trigger when srcport is in the range of 50000 to 50007.

The attributes below are optional.

If the srcport label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

dstport

Used as a requisite to trigger a rule. It will check the destination port (decoded as dstport).

The attributes below are optional.

If the dstport label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

data

Used as a requirement to trigger a rule, it compares a regular expression representing a data with a value decoded as data.

The attributes below are optional.

If the data label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

extra_data

Used as a requirement to trigger a rule, it compares a regular expression representing a data with a value decoded as extra_data.

Example:

<rule id="7301" level="0">
  <category>windows</category>
  <extra_data>^Symantec AntiVirus</extra_data>
  <description>Grouping of Symantec AV rules from eventlog.</description>
</rule>

This rule will trigger when the log belongs to windows category and the decoded field extra_data is: Symantec AntiVirus

The attributes below are optional.

If the extra_data label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

user

Used as a requirement to trigger a rule, it compares a regular expression representing a user with a value decoded as user.

Example:

May  9 08:58:13 my-server sudo[3856]: pam_unix(sudo:session): session opened for user foo by vagrant(uid=1000)

<rule id="140101" level="12">
  <if_group>authentication_success</if_group>
  <user negate="yes">wazuh|root</user>
  <description>Unexpected user successfully logged to the system.</description>
</rule>

This rule triggers when a user different from root or wazuh successfully logs in to the system.

The attributes below are optional.

If the user label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

system_name

Used as a requirement to trigger a rule, it compares a regular expression representing a system name with a value decoded as system_name.

The attributes below are optional.

If the system_name label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

program_name

Used as a requirement to trigger a rule, it compares a regular expression representing a program name with a value decoded as program_name.

Example:

<rule id="1005" level="5">
  <program_name>syslogd</program_name>
  <match>^restart</match>
  <description>Syslogd restarted.</description>
  <group>pci_dss_10.6.1,gpg13_10.1,gpg13_4.14,gdpr_IV_35.7.d,hipaa_164.312.b,nist_800_53_AU.6,</group>
</rule>

The rule will trigger when the program Syslogd is restarted.

The attributes below are optional.

If the program_name label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

protocol

Used as a requirement to trigger a rule, it compares a regular expression representing a protocol with a value decoded as protocol.

The attributes below are optional.

If the protocol label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

hostname

Used as a requirement to trigger a rule, it compares a regular expression representing a hostname with a value decoded as hostname.

Example:

<rule id="2931" level="0">
  <hostname>yum.log$</hostname>
  <match>^Installed|^Updated|^Erased</match>
  <description>Yum logs.</description>
</rule>

This rule will group rules for Yum logs when something is either being installed, updated or erased.

The attributes below are optional.

If the hostname label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

time

Used as a requisite to trigger a rule. It checks the event time based on the Wazuh server time, not the event timestamp. You must configure local time settings correctly to prevent unexpected triggers.

Example:

<rule id="17101" level="9">
  <if_group>authentication_success</if_group>
  <time>6 pm - 8:30 am</time>
  <description>Successful login during non-business hours.</description>
  <group>login_time,pci_dss_10.2.5,pci_dss_10.6.1,gpg13_7.1,gpg13_7.2,gdpr_IV_35.7.d,gdpr_IV_32.2,hipaa_164.312.b,nist_800_53_AU.14,nist_800_53_AC.7,nist_800_53_AU.6,</group>
</rule>

This rule triggers on successful logins occurring between 6 PM and 8 AM Wazuh server time.

weekday

Used as a requisite to trigger a rule. It checks the event weekday based on the Wazuh server time, not the event timestamp. You must configure local time settings correctly to prevent unexpected triggers.

Example:

<rule id="17102" level="9">
  <if_group>authentication_success</if_group>
  <weekday>weekends</weekday>
  <description>Successful login during weekend.</description>
  <group>login_day,pci_dss_10.2.5,pci_dss_10.6.1,gpg13_7.1,gpg13_7.2,gdpr_IV_35.7.d,gdpr_IV_32.2,hipaa_164.312.b,nist_800_53_AU.14,nist_800_53_AC.7,nist_800_53_AU.6,</group>
</rule>

This rule triggers on successful logins during the weekend.

id

Used as a requisite to trigger a rule. It compares a regular expression that represents an ID with a value decoded as id.

Example:

Feb  3 10:23:08 testsys kernel: usb 1-1.2: New USB device found, idVendor=0781, idProduct=5575

<rule id="81100" level="0">
    <decoded_as>kernel</decoded_as>
    <id>usb</id>
    <description>USB messages grouped.</description>
</rule>

This rule will check the content of the field id and group the logs whose decoded ID is usb.

The attributes below are optional.

If the id label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

url

Used as a requisite to trigger a rule. It compares a regular expression representing a URL with a value decoded as url.

Example:

<rule id="31102" level="0">
  <if_sid>31101</if_sid>
  <url>.jpg$|.gif$|favicon.ico$|.png$|robots.txt$|.css$|.js$|.jpeg$</url>
  <compiled_rule>is_simple_http_request</compiled_rule>
  <description>Ignored extensions on 400 error codes.</description>
</rule>

This rule is a child from a level 5 rule 31101 and becomes a level 0 rule when it confirms that the extensions are benign.

The attributes below are optional.

If the url label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

location

Used as a requisite to trigger a rule. It will check the content of the field location and try to find a match.

The location identifies the origin of the input. If the event comes from an agent, its name and registered IP address (as it was added) is appended to the location.

Example of a location for a log pulled from /var/log/syslog in an agent with name dbserver and registered with IP any:

(dbserver) any->/var/log/syslog

The following components use a static location:

Example:

<rule id="24000" level="3">
  <location>osquery$</location>
  <description>osquery message</description>
</rule>

This rule groups logs that come from the osquery location.

The attributes below are optional.

If the location label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

action

Used as a requirement to trigger a rule, it compares a regular expression representing an action with a value decoded as action.

Example:

<rule id="4502" level="4">
  <if_sid>4500</if_sid>
  <action type="osregex">warning|WARN</action>
  <description>Netscreen warning message.</description>
</rule>

This rule will trigger a level 4 alert when the decoded action from Netscreen is warning or WARN.

The attributes below are optional.

If the action label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

status

Compares a regular expression representing a status with a value decoded as status.

Example:

<rule id="213" level="7">
  <if_sid>210</if_sid>
  <status>aborted</status>
  <description>Remote upgrade could not be launched. Error: $(error).</description>
  <group>upgrade,upgrade_failure,</group>
</rule>

The attributes below are optional.

If the status label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

srcgeoip

Used as a requirement to trigger a rule, it compares a regular expression representing a source GeoIP with a value decoded as srcgeoip.

The attributes below are optional.

If the srcgeoip label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

dstgeoip

Used as a requirement to trigger a rule, it compares a regular expression representing a destination GeoIP with a value decoded as dstgeoip.

The attributes below are optional.

If the dstgeoip label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value is used.

if_sid

Used as a requisite to trigger a rule. This option matches if the log has previously matched a rule in the specified ID. It is similar to a child decoder, with the key difference that alerts can have as many descendants as necessary, whereas decoders cannot have "grandchildren".

Example:

<rule id="100110" level="5">
  <if_sid>100100, 100101</if_sid>
  <match>Error</match>
  <description>There is an error in the log.</description>
</rule>

The rule 100110 is triggered when either of the parent rules has matched and the logs contain the word Error.

if_group

Used as a requisite to trigger a rule. This option matches if the log has previously matched a rule in the specified group.

Example:

<rule id="184676" level="12">
    <if_group>sysmon_event1</if_group>
    <field name="sysmon.image">lsm.exe</field>
    <description>Sysmon - Suspicious Process - lsm.exe</description>
    <group>pci_dss_10.6.1,pci_dss_11.4,gdpr_IV_35.7.d,hipaa_164.312.b,nist_800_53_AU.6,nist_800_53_SI.4,</group>
</rule>

The rule matches if the log has previously matched a rule in the sysmon_event1 group and if the decoded field sysmon.image contains the value lsm.exe.

if_level

Matches if the level has matched before.

if_matched_sid

Matches if an alert of the defined ID has been triggered in a set number of seconds.

This option is used in conjunction with frequency and timeframe.

Example:

<rule id="30316" level="10" frequency="10" timeframe="120">
  <if_matched_sid>30315</if_matched_sid>
  <same_source_ip />
  <description>Apache: Multiple Invalid URI requests from same source.</description>
  <mitre>
    <id>T1499</id>
  </mitre>
  <group>gdpr_IV_35.7.d,hipaa_164.312.b,invalid_request,nist_800_53_AU.14,nist_800_53_AC.7,nist_800_53_SI.4,pci_dss_10.2.4,pci_dss_11.4,tsc_CC6.1,tsc_CC6.8,tsc_CC7.2,tsc_CC7.3,</group>
</rule>

The rule is triggered when rule 30315 has been triggered 10 times in 120 seconds and if the requests were made by the same srcip.

if_matched_group

Matches if an alert of the defined group has been triggered in a set number of seconds.

This option is used in conjunction with frequency and timeframe.

Example:

<rule id="40113" level="12" frequency="8" timeframe="360">
  <if_matched_group>virus</if_matched_group>
  <description>Multiple viruses detected - Possible outbreak.</description>
  <group>virus,pci_dss_5.1,pci_dss_5.2,pci_dss_11.4,gpg13_4.2,gdpr_IV_35.7.d,nist_800_53_SI.3,nist_800_53_SI.4,</group>
</rule>

The rule will trigger when the group virus has been matched 8 times in the last 360 seconds.

if_fts

Makes the decoder that processed the event to take the fts line into consideration.

same_id

Specifies that the decoded ID must be the same. This option is used in conjunction with frequency and timeframe.

different_id

Specifies that the decoded id must be different. This option is used in conjunction with frequency and timeframe.

same_srcip

Specifies that the decoded source IP address must be the same. This option is used in conjunction with frequency and timeframe.

The deprecated label same_source_ip works like an alias for same_srcip.

different_srcip

Specifies that the decoded source IP address must be different. This option is used in conjunction with frequency and timeframe.

The deprecated label not_same_source_ip works like an alias for different_srcip.

same_dstip

Specifies that the decoded destination IP address must be the same. This option is used in conjunction with frequency and timeframe.

different_dstip

Specifies that the decoded destination IP address must be different. This option is used in conjunction with frequency and timeframe.

same_srcport

Specifies that the decoded source port must be the same. This option is used in conjunction with frequency and timeframe.

different_srcport

Specifies that the decoded source port must be different. This option is used in conjunction with frequency and timeframe.

same_dstport

Specifies that the decoded destination port must be the same. This option is used in conjunction with frequency and timeframe.

different_dstport

Specifies that the decoded destination port must be different. This option is used in conjunction with frequency and timeframe.

same_location

Specifies that the location must be the same. This option is used in conjunction with frequency and timeframe.

different_location

Specifies that the decoded location must be different. This option is used in conjunction with frequency and timeframe.

same_srcuser

Specifies that the decoded source user must be the same. This option is used in conjunction with frequency and timeframe.

different_srcuser

Specifies that the decoded source user must be different. This option is used in conjunction with frequency and timeframe.

same_user

Specifies that the decoded user must be the same. This option is used in conjunction with frequency and timeframe.

different_user

Specifies that the decoded user must be different. This option is used in conjunction with frequency and timeframe.

same_field

The value of the dynamic field specified in this option must appear a certain number of times in previous events, as defined by the frequency attribute, within a time frame specified by the timeframe attribute.

As an example of this option, check these rules:

<!-- {"key":"value", "key2":"AAAA"} -->
<rule id="100001" level="3">
  <decoded_as>json</decoded_as>
  <field name="key">value</field>
  <description>Testing JSON alert</description>
</rule>

<rule id="100002" level="10" frequency="4" timeframe="300">
  <if_matched_sid>100001</if_matched_sid>
  <same_field>key2</same_field>
  <description>Testing same_field option</description>
</rule>

Rule 100002 will fire when key2 in the currently considered event is the same in four events that matched rule 100001 within the last 300 seconds. Consider the following event logs generated in less than 300 seconds:

{"key":"value", "key2":"AAAA"}
{"key":"value", "key2":"AAAA"}
{"key":"value", "key2":"BBBB"}
{"key":"value", "key2":"AAAA"}
{"key":"value", "key2":"CCCC"}
{"key":"value", "key2":"CCCC"}
{"key":"value", "key2":"AAAA"}

The last event will fire rule 100002 instead of 100001 because it found the value AAAA in three of the previous events. The corresponding alert looks like the following:

{
  "timestamp": "2020-03-04T03:00:28.973-0800",
  "rule": {
    "level": 10,
   "description": "Testing same_field option",
   "id": "100002",
    "frequency": 4,
    "firedtimes": 1,
    "mail": false,
    "groups": [
      "local"
    ]
  },
  "agent": {
    "id": "000",
    "name": "ubuntu"
  },
  "manager": {
    "name": "ubuntu"
  },
  "id": "1583319628.14426",
  "previous_output": "{\"key\":\"value\",\"key2\":\"AAAA\"}\n{\"key\":\"value\",\"key2\":\"AAAA\"}\n{\"key\":\"value\",\"key2\":\"AAAA\"}",
  "full_log": "{\"key\":\"value\",\"key2\":\"AAAA\"}",
  "decoder": {
    "name": "json"
  },
  "data": {
    "key": "value",
    "key2": "AAAA"
  },
  "location": "/root/test.log"
}

different_field

It is the opposite setting of same_field. The value of the dynamic field specified in this option must differ from those found in previous events a certain number of times. This is defined by the frequency attribute, within a time frame specified by the timeframe attribute.

global_frequency

Specifies that the events of all agents will be contemplated when using the frequency and timeframe options. By default, only the events generated by the same agent will be taken into account to increase the frequency counter for a rule.

same_protocol

Specifies that the decoded protocol must be the same. This option is used in conjunction with frequency and timeframe.

different_protocol

Specifies that the decoded protocol must be different. This option is used in conjunction with frequency and timeframe.

same_action

Specifies that the decoded action must be the same. This option is used in conjunction with frequency and timeframe.

different_action

Specifies that the decoded data must be the same. This option is used in conjunction with frequency and timeframe.

same_data

Specifies that the decoded data must be the same. This option is used in conjunction with frequency and timeframe.

different_data

Specifies that the decoded data must be different. This option is used in conjunction with frequency and timeframe.

same_extra_data

Specifies that the decoded extra data must be the same. This option is used in conjunction with frequency and timeframe.

different_extra_data

Specifies that the decoded extra data must be different. This option is used in conjunction with frequency and timeframe.

same_status

Specifies that the decoded status must be the same. This option is used in conjunction with frequency and timeframe.

different_status

Specifies that the decoded status must be different. This option is used in conjunction with frequency and timeframe.

same_system_name

Specifies that the decoded system name must be the same. This option is used in conjunction with frequency and timeframe.

different_system_name

Specifies that the decoded system name must be different. This option is used in conjunction with frequency and timeframe.

same_url

Specifies that the decoded url must be the same. This option is used in conjunction with frequency and timeframe.

different_url

Specifies that the decoded url must be different. This option is used in conjunction with frequency and timeframe.

same_srcgeoip

Specifies that the source GeoIP location must be the same. This option is used in conjunction with frequency and timeframe.

different_srcgeoip

Specifies that the source GeoIP location must be different. This option is used in conjunction with frequency and timeframe.

Example:

As an example of these last options, check this rule:

<rule id=100005 level="0">
  <match> Could not open /home </match>
  <same_user />
  <different_srcgeoip />
  <same_dstport />
</rule>

The rule filters when the same user tries to open file /home but returns an error, on a different GeoIP and using the same destination port.

same_dstgeoip

Specifies that the destination GeoIP location must be the same. This option is used in conjunction with frequency and timeframe.

different_dstgeoip

Specifies that the destination GeoIP location must be different. This option is used in conjunction with frequency and timeframe.

description

Specifies a human-readable description of the rule to provide context to each alert regarding the nature of the events matched by it.

Examples:

<rule id="100015" level="2">
  ...
  <description>A timeout occurred.</description>
</rule>

<rule id="100035" level="4">
  ...
  <description>File missing. Root access unrestricted.</description>
</rule>

Since Wazuh version 3.3, it is possible to include any decoded field (static or dynamic) to the description message. You can use the following syntax: $(field_name) to add a field to the description.

Example:

<rule id="100005" level="8">
  <match>illegal user|invalid user</match>
  <description>sshd: Attempt to login using a non-existent user from IP $(attempt_ip)</description>
  <options>no_log</options>
</rule>

If description label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

list

Perform a Constant DataBase lookup using a CDB list. This is a fast on-disk database which will always find keys within two seeks of the file.

Example:

<rule id="80780" level="3">
    <if_sid>80700</if_sid>
    <list field="audit.key" lookup="match_key_value" check_value="write">etc/lists/audit-keys</list>
    <description>Audit: Watch - Write access</description>
    <group>audit_watch_write,gdpr_IV_30.1.g,</group>
</rule>

The rule will look for audit.key in the CDB list. Where it will check if it is equal to write, in which case it will match and trigger a level 3 alert.

info

You can add extra information through the following attributes:

Example:

<rule id="5714" level="14" timeframe="120" frequency="3">
  <if_matched_sid>5713</if_matched_sid>
  <match>Local: crc32 compensation attack</match>
  <description>sshd: SSH CRC-32 Compensation attack</description>
  <info type="cve">2001-0144</info>
  <info type="link">http://www.securityfocus.com/bid/2347/info/</info>
  <group>exploit_attempt,pci_dss_11.4,pci_dss_6.2,gpg13_4.12,gdpr_IV_35.7.d,nist_800_53_SI.4,nist_800_53_SI.2,</group>
</rule>

The rule provides additional information about the threat it detects.

options

Additional rule options.

Example:

<rule id="9800" level="8">
  <match>illegal user|invalid user</match>
  <description>sshd: Attempt to login using a non-existent user</description>
  <options>no_log</options>
</rule>

check_diff

Used to determine when the output of a command changes.

Example:

<rule id="534" level="1">
  <if_sid>530</if_sid>
  <match>ossec: output: 'w'</match>
  <check_diff />
  <options>no_log</options>
  <description>List of logged in users. It will not be alerted by default.</description>
</rule>

mitre

Specifies the MITRE ATT&CK technique ID or IDs that fit in well with the rule.

Example:

<rule id="100002" level="10">
  <description>Attack technique sample.</description>
  <mitre>
    <id>T1110</id>
    <id>T1037</id>
  </mitre>
</rule>

var

Defines a variable that can be used in any rule within the same rule file. It must be defined at the base level of the rule file, not inside a tagged section.

Example:

<var name="joe_folder">/home/joe/</var>

<group name="local,">

   <rule id="100001" level="5">
     <if_sid>550</if_sid>
    <field name="file">^$joe_folder</field>
    <description>A Joe's file was modified.</description>
     <group>ossec,pci_dss_10.6.1,gpg13_10.1,gdpr_IV_35.7.d,</group>
   </rule>

</group>

<var name="BAD_WORDS">error|warning|failure</var>

<var name="BAD_WORDS">error|warning|failure</var>
<group name="syslog,errors,">
  <rule id="XXXX" level="2">
   <match>$BAD_WORDS</match>
   <description>Error found.</description>
  </rule>
</group>