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 (either in source code or compiled form) and the target to be scanned. The target can be a file, a folder, or a process.

yara [OPTIONS] RULES_FILE TARGET

RULES_FILE can be passed directly in source code form, or can be previously compiled with the yarac tool. You may prefer to use your rules in compiled form if you are going to invoke YARA multiple times with the same rules. This way you’ll 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:

-t <tag> --tag=<tag>

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

-i <identifier> --identifier=<identifier>

Print rules named <identifier> and ignore the rest.

-c --count

Print only number of matches.

-n

Print not satisfied rules only (negate).

-D --print-module-data

Print module data.

-g --print-tags

Print tags.

-m --print-meta

Print metadata.

-s --print-strings

Print matching strings.

-L --print-string-length

Print length of matching strings.

-e --print-namespace

Print rules’ namespace.

-p <number> --threads=<number>

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

-l <number> --max-rules=<number>

Abort scanning after matching a number of rules.

-a <seconds> --timeout=<seconds>

Abort scanning after a number of seconds has elapsed.

-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.

New in version 3.5.0.

--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.

New in version 3.7.0.

-d <identifier>=<value>

Define external variable.

-x <module>=<file>

Pass file’s content as extra data to module.

-r --recursive

Recursively search for directories.

-f --fast-scan

Fast matching mode.

-w --no-warnings

Disable warnings.

--fail-on-warnings

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

-v --version

Show version information.

-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 -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