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Running YARA from the command-line

In order to invoke YARA you’ll need two things: a file with the rules you want to use and the target to be scanned. The target can be a file, a folder, or a process.

yara [OPTIONS] RULES_FILE TARGET

In YARA 3.8 and below RULES_FILE was allowed to be a file with rules in source form or in compiled form indistinctly. In YARA 3.9 you need to explictly specify that RULES_FILE contains compiled rules by using the -C flag.

yara [OPTIONS] -C RULES_FILE TARGET

This is a security measure to prevent users from inadvertenly using compiled rules coming from a third-party. Using compiled rules from untrusted sources can lead to the execution of malicious code in your computer.

For compiling rules beforhand you can use the yarac tool. This way can save time, because for YARA it is faster to load compiled rules than compiling the same rules over and over again.

You can also pass multiple source files to yara like in the following example:

yara [OPTIONS] RULES_FILE_1 RULES_FILE_2 RULES_FILE_3 TARGET

Notice however that this only works for rules in source form. When invoking YARA with compiled rules a single file is accepted.

In the example above all rules share the same "default" namespace, which means that rule identifiers must be unique among all files. However you can specify a namespace for individual files. For example

yara [OPTIONS] namespace1:RULES_FILE_1 RULES_FILE_2 RULES_FILE_3 TARGET

In this case RULE_FILE_1 uses namespace1 while RULES_FILE_2 and RULES_FILE_3 share the default namespace.

In all cases rules will be applied to the target specified as the last argument to YARA, if it’s a path to a directory all the files contained in it will be scanned. By default YARA does not attempt to scan directories recursively, but you can use the -r option for that.

Available options are:

.. program:: yara

.. option:: -t <tag> --tag=<tag>

  Print rules tagged as <tag> and ignore the rest.

.. option:: -i <identifier> --identifier=<identifier>

  Print rules named <identifier> and ignore the rest.

.. option:: -C --compiled-rules

  RULES_FILE contains rules already compiled with yarac.

.. option:: -c --count

  Print only number of matches.

.. option:: -n

  Print not satisfied rules only (negate).

.. option:: -D --print-module-data

  Print module data.

.. option:: -g --print-tags

  Print tags.

.. option:: -m --print-meta

  Print metadata.

.. option:: -s --print-strings

  Print matching strings.

.. option:: -L --print-string-length

  Print length of matching strings.

.. option:: -e --print-namespace

  Print rules' namespace.

.. option:: -p <number> --threads=<number>

  Use the specified <number> of threads to scan a directory.

.. option:: -l <number> --max-rules=<number>

  Abort scanning after matching a number of rules.

.. option:: -a <seconds> --timeout=<seconds>

  Abort scanning after a number of seconds has elapsed.

.. option:: -k <slots> --stack-size=<slots>

  Allocate a stack size of "slots" number of slots. Default: 16384. This
  will allow you to use larger rules, albeit with more memory overhead.

  .. versionadded:: 3.5.0

.. option:: --max-strings-per-rule=<number>

  Set maximum number of strings per rule (default=10000). If a rule has more
  then the specified number of strings an error will occur.

  .. versionadded:: 3.7.0

.. option:: -d <identifier>=<value>

  Define external variable.

.. option:: -x <module>=<file>

  Pass file's content as extra data to module.

.. option:: -r --recursive

  Recursively search for directories.

.. option:: -f --fast-scan

  Fast matching mode.

.. option:: -w --no-warnings

  Disable warnings.

.. option:: --fail-on-warnings

  Treat warnings as errors. Has no effect if used with --no-warnings.

.. option:: -v --version

  Show version information.

.. option:: -h --help

  Show help.

Here you have some examples:

  • Apply rule in /foo/bar/rules to all files in the current directory. Subdirectories are not scanned:

    yara /foo/bar/rules  .
    
  • Apply rules in /foo/bar/rules to bazfile. Only reports rules tagged as Packer or Compiler:

    yara -t Packer -t Compiler /foo/bar/rules bazfile
    
  • Scan all files in the /foo directory and its subdirectories:

    yara /foo/bar/rules -r /foo
    
  • Defines three external variables mybool, myint and mystring:

    yara -d mybool=true -d myint=5 -d mystring="my string" /foo/bar/rules bazfile
    
  • Apply rules in /foo/bar/rules to bazfile while passing the content of cuckoo_json_report to the cuckoo module:

    yara -x cuckoo=cuckoo_json_report /foo/bar/rules bazfile
    
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