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File Integrity Module

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File Integrity Module

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The file_integrity module sends events when a file is changed (created, updated, or deleted) on disk. The events contain file metadata and hashes.

The module is implemented for Linux, macOS (Darwin), and Windows.

How it works

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This module uses features of the operating system to monitor file changes in realtime. When the module starts it creates a subscription with the OS to receive notifications of changes to the specified files or directories. Upon receiving notification of a change the module will read the file’s metadata and the compute a hash of the file’s contents.

At startup this module will perform an initial scan of the configured files and directories to generate baseline data for the monitored paths and detect changes since the last time it was run. It uses locally persisted data in order to only send events for new or modified files.

The operating system features that power this feature are as follows.

Linux - inotify is used, and therefore the kernel must have inotify support. Inotify was initially merged into the 2.6.13 Linux kernel.
macOS (Darwin) - Uses the FSEvents API, present since macOS 10.5. This API coalesces multiple changes to a file into a single event. Auditbeat translates this coalesced changes into a meaningful sequence of actions. However, in rare situations the reported events may have a different ordering than what actually happened.
Windows - ReadDirectoryChangesW is used.

The file integrity module should not be used to monitor paths on network file systems.

Configuration options

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This module has some configuration options for tuning its behavior. The following example shows all configuration options with their default values for Linux.

- module: file_integrity
  paths:
  - /bin
  - /usr/bin
  - /sbin
  - /usr/sbin
  - /etc
  exclude_files:
  - '(?i)\.sw[nop]$'
  - '~$'
  - '/\.git($|/)'
  include_files: []
  scan_at_start: true
  scan_rate_per_sec: 50 MiB
  max_file_size: 100 MiB
  hash_types: [sha1]
  recursive: false

This module also supports the standard configuration options described later.

paths

A list of paths (directories or files) to watch. Globs are not supported. The specified paths should exist when the metricset is started. Paths should be absolute, although the file integrity module will attempt to resolve relative path events to their absolute file path. Symbolic links will be resolved on module start and the link target will be watched if link resolution is successful. Changes to the symbolic link after module start will not change the watch target. If the link does not resolve to a valid target, the symbolic link itself will be watched; if the symlink target becomes valid after module start up this will not be picked up by the file system watches.

exclude_files

A list of regular expressions used to filter out events for unwanted files. The expressions are matched against the full path of every file and directory. When used in conjunction with include_files, file paths need to match both include_files and not match exclude_files to be selected. By default, no files are excluded. See Regular expression support for a list of supported regexp patterns. It is recommended to wrap regular expressions in single quotation marks to avoid issues with YAML escaping rules.

include_files

A list of regular expressions used to specify which files to select. When configured, only files matching the pattern will be monitored. The expressions are matched against the full path of every file and directory. When used in conjunction with exclude_files, file paths need to match both include_files and not match exclude_files to be selected. By default, all files are selected. See Regular expression support for a list of supported regexp patterns. It is recommended to wrap regular expressions in single quotation marks to avoid issues with YAML escaping rules.

scan_at_start

A boolean value that controls if Auditbeat scans over the configured file paths at startup and send events for the files that have been modified since the last time Auditbeat was running. The default value is true.

This feature depends on data stored locally in path.data in order to determine if a file has changed. The first time Auditbeat runs it will send an event for each file it encounters.

scan_rate_per_sec

When scan_at_start is enabled this sets an average read rate defined in bytes per second for the initial scan. This throttles the amount of CPU and I/O that Auditbeat consumes at startup. The default value is "50 MiB". Setting the value to "0" disables throttling. For convenience units can be specified as a suffix to the value. The supported units are b (default), kib, kb, mib, mb, gib, gb, tib, tb, pib, pb, eib, and eb.

max_file_size

The maximum size of a file in bytes for which Auditbeat will compute hashes and run file parsers. Files larger than this size will not be hashed or analysed by configured file parsers. The default value is 100 MiB. For convenience, units can be specified as a suffix to the value. The supported units are b (default), kib, kb, mib, mb, gib, gb, tib, tb, pib, pb, eib, and eb.

hash_types

A list of hash types to compute when the file changes. The supported hash types are blake2b_256, blake2b_384, blake2b_512, md5, sha1, sha224, sha256, sha384, sha512, sha512_224, sha512_256, sha3_224, sha3_256, sha3_384, sha3_512, and xxh64. The default value is sha1.

file_parsers

A list of file_integrity fields under file that will be populated by file format parsers. The available fields that can be analysed are listed in the auditbeat.reference.yml file. File parsers are run on all files within the max_file_size limit in the configured paths during a scan or when a file event involves the file. Files that are not targets of the specific file parser are only sniffed to examine whether analysis should proceed. This will usually only involve reading a small number of bytes.

recursive

By default, the watches set to the paths specified in paths are not recursive. This means that only changes to the contents of this directories are watched. If recursive is set to true, the file_integrity module will watch for changes on this directories and all their subdirectories.

Standard configuration options

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You can specify the following options for any Auditbeat module.

module

The name of the module to run.

enabled

A Boolean value that specifies whether the module is enabled.

fields

A dictionary of fields that will be sent with the dataset event. This setting is optional.

tags

A list of tags that will be sent with the dataset event. This setting is optional.

processors

A list of processors to apply to the data generated by the dataset.

See Processors for information about specifying processors in your config.

index

If present, this formatted string overrides the index for events from this module (for elasticsearch outputs), or sets the raw_index field of the event’s metadata (for other outputs). This string can only refer to the agent name and version and the event timestamp; for access to dynamic fields, use output.elasticsearch.index or a processor.

Example value: "%{[agent.name]}-myindex-%{+yyyy.MM.dd}" might expand to "auditbeat-myindex-2019.12.13".

keep_null

If this option is set to true, fields with null values will be published in the output document. By default, keep_null is set to false.

service.name

A name given by the user to the service the data is collected from. It can be used for example to identify information collected from nodes of different clusters with the same service.type.

Example configuration

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The File Integrity module supports the common configuration options that are described under configuring Auditbeat. Here is an example configuration:

auditbeat.modules:
- module: file_integrity
  paths:
  - /bin
  - /usr/bin
  - /sbin
  - /usr/sbin
  - /etc

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