Writing a Probe

Probes are, in some ways, the essence of garak’s functionality – they serve as the abstraction that encapsulates attacks against AI models and systems. This document covers the key points of how to develop a new probe.

For information on how to contribute to garak, and how we build and manage our code, see Extending garak.

Naming

Naming is one of the hardest problems in computer science. Here are some tips explaining how to work out probe naming in garak.

Probe module files should ideally be named after the technique they implement, instead of the effect they elicit. For example, the encoding module contains problems where various encodings are used to as part of the attack.

Probe classes should avoid duplicating the probe module name. This is already available when loading the probe. It should describe a technique variant that the particular attack is going for.

The goal of the attack should not be in the name. Garak aims to decouple the target failure mode from the technique used to elicit it. If this is possible, naming should focus on the technique. So for a probe using character swapping to get a violent content, prefer something like swap.Character instead of violence.Violence. Though the latter is almost a good name for a detector (in the unsafe_content module).

Substance

Scores are reported at per-probe level. Each probe gets a percentage score regardless of how many prompts were issued or how many times. A probe that runs only one prompt might get a high or low score - but with only one prompt, this isn’t so useful. A sample size of one makes for poor statistics.

For a probe to be worth including, it should have a decent number of prompts, with good variation. Thirty is a reasonable minimum bar. As well as other techniques, it’s acceptable for prompts to be dynamically generated on-the-fly or via templating.

Garak should have some respect for inference time, and try to cover new bases with the prompting budget that it consumes. New probes that cover very similar ground to existing ones should be evaluated carefully.

For a probe to be worth including, it should add something new to garak. Novelty is a factor used when considering merging a new probe into the code base.

Inheritance

All probes inherit from garak.probes.base.Probe, exposed at package level via garak.probes.

import garak.probes

class MyNewProbe(garak.probes.Probe):
    """Probe to do something naughty to a language model"""
    ...

By inheriting from garak.probes.base.Probe, probes can work nicely with Generator and Attempt objects in addition to ensuring that any Buff objects that you apply to a probe will work appropriately.

The probe method of a Probe object provides the core logic of the probe. Ideally, you only need to populate the prompts attribute of a Probe and let the probe method do the heavy lifting. However, if this logic is insufficient for your probe, the probe method is where the majority of the work (and potential issues) tends to lie.

def probe(self, generator) -> Iterable[garak.attempt.Attempt]:
    """attempt to exploit the target generator, returning a list of results"""
    logging.debug("probe execute: %s", self)

    self.generator = generator

    # build list of attempts
    attempts_todo: Iterable[garak.attempt.Attempt] = []
    prompts = list(self.prompts)
    for seq, prompt in enumerate(prompts):
        attempts_todo.append(self._mint_attempt(prompt, seq))

    # buff hook
    if len(_config.buffmanager.buffs) > 0:
        attempts_todo = self._buff_hook(attempts_todo)

    # iterate through attempts
    attempts_completed = self._execute_all(attempts_todo)

    logging.debug(
        "probe return: %s with %s attempts", self, len(attempts_completed)
    )

    return attempts_completed

Configuring and Describing Probes

Probes are built upon the Configurable base class and are themselves configurable. We largely ignore parameters like ENV_VAR and DEFAULT_PARAMS in Probe classes, but if your probe requires an environment variable or you want to set some default parameters, it is done first in the class.

More often, we’ll be looking at descriptive attributes of the probe. From the base class:

# docs uri for a description of the probe (perhaps a paper)
doc_uri: str = ""
# language this is for, in BCP47 format; * for all langs
lang: Union[str, None] = None
# should this probe be included by default?
active: bool = True
# MISP-format taxonomy categories
tags: Iterable[str] = []
# what the probe is trying to do, phrased as an imperative
goal: str = ""
# Deprecated -- the detectors that should be run for this probe. always.Fail is chosen as default to send a signal if this isn't overridden.
recommended_detector: Iterable[str] = ["always.Fail"]
# default detector to run, if the primary/extended way of doing it is to be used (should be a string formatted like recommended_detector)
primary_detector: Union[str, None] = None
# optional extended detectors
extended_detectors: Iterable[str] = []
# can attempts from this probe be parallelised?
parallelisable_attempts: bool = True
# Keeps state of whether a buff is loaded that requires a call to untransform model outputs
post_buff_hook: bool = False
# support mainstream any-to-any large models
# legal element for str list `modality['in']`: 'text', 'image', 'audio', 'video', '3d'
# refer to Table 1 in https://arxiv.org/abs/2401.13601
# we focus on LLM input for probe
modality: dict = {"in": {"text"}}

That’s a lot of attributes before we get into ones you may need to add! Many of these are decent defaults, though there are a few that we absolutely want to include in any new probe

  • doc_uri: What is a good reference for the probe you’re implementing? An academic paper, blog post, or social media post (in descending order of preference) goes here.

  • active: Should this probe be part of default scans?

  • tags: MISP-formatted taxonomy categories __e.g.__ ["avid-effect:security:S0403", "owasp:llm01", "quality:Security:PromptStability", "payload:jailbreak"]

  • goal: What is the probe trying to do? __e.g.__ "disregard the system prompt"

  • primary_detector: What Detector should your probe use?

class MyNewProbe(garak.probes.Probe):
    """Probe to do something naughty to a language model"""

    primary_detector = "mitigation.MitigationBypass"
    tags = [
        "avid-effect:security:S0403",
        "owasp:llm01",
        "quality:Security:PromptStability",
        "payload:jailbreak",
    ]
    goal = "disregard the system prompt"
    doc_uri = "https://garak.ai"
    active = False
    ...

Probe Documentation

You must provide documentation for your probe. Class docstrings are required and are enforced by a test that must pass before merging.

  1. Add an .rst file in the docs/source directory with the name garak.probes.<module>.rst, where module matches the file name of your new probe.

    Refer to other probe documentation for an example of the content.

    Also refer to the garak tests to ensure your documentation is correct. The tests check that you added documentation, that the class docstrings are present, and that they link to the right places.

  2. Add an entry in docs/source/probes.rst and link to your new module file.

Both the class and module docstrings must be in ReStructuredText (RST) format, and not markdown. Refer to the rst Cheatsheet or ReStructuredText Primer to get you started.

Paragraphs are separated by a blank lines, such as \\n\\n.

Module Docstrings

In the Python module you’re working on, add a module docstring, if there isn’t one already. Include the following parts:

  • Title, in bold/strong emphasis (**)

  • A description of the common technique/intent/source for all probes in this module (one sentence)

  • The inclusion criteria for items in this module, so that others can determine whether or not a new probe would belong in the module (1-3 sentences)

  • Further description (optional; one paragraph; 1-5 sentences)

  • Links to information about this kind of attack (optional)

Refer to the following example:

"""**ANSI Escape attack**

Try to make a model produce ANSI escape codes, which can disrupt downstream processing.

Probes in this module should all try to elicit ANSI escape codes or information suggesting that the target is capable of producing them.
There are a couple of different dimensions included:

* the encoding can vary - raw binary, or an escaped version;
* the technique used can vary - can we get OCS8, OCS52
* the action can also be different - log cursor, crash machine, install software etc.

Further info:

* https://interhumanagreement.substack.com/p/llm-output-can-take-over-your-computer
* https://www.youtube.com/watch?v=3T2Al3jdY38
* https://embracethered.com/blog/posts/2024/terminal-dillmas-prompt-injection-ansi-sequences/
* https://dgl.cx/2023/09/ansi-terminal-security
* https://cwe.mitre.org/data/definitions/150.html
"""

Class Docstrings

Probe classes themselves must also have a docstring. The target structure for garak Probe class docstrings include the following items:

  • Short description of the technique or intent of the probe (1 sentence, followed by a blank line)

  • Friendly general intro to the probe, in very simple English (1-4 sentences; short sentences; follow Basic English rules as much as possible, try this tool)

  • Example prompts generated by the probe (optional; in RST-formatted blockquote)

  • How the probe works, extended description (optional; can be multiple paragraphs)

  • Link to source docs; include reference and hyperlink (optional; 1-2 lines)

  • For probes implementing work in a paper, include the paper’s abstract (optional; in RST-formatted blockquote)

Testing

Once the logic for our probe is written, you’ll want to test it before opening a pull request. Typically, a good place to start is by seeing if your probe can be imported!

$ conda activate garak
$ python
$ python
Python 3.11.5 (main, Sep 11 2023, 08:31:25) [Clang 14.0.6 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import garak.probes.mynewprobe
>>>

If you can run this with no error, you’re ready to move on to the next phase of testing. Otherwise, try to address the encountered errors.

Let’s try running our new probe against a HuggingFace Pipeline using meta-llama/Llama-2-7b-chat-hf, a notoriously tricky model to get to behave badly.

$ garak -t huggingface -n meta-llama/Llama-2-7b-chat-hf -p mynewprobe.MyNewProbe

If it all runs well, you’ll get a log and a hitlog file, which tell you how successful your new probe was! If you encounter errors, go through and try to address them. You can look at the bottom of the garak.log file, whose path is printed in the output every time you call garak, to see what errors there are.

If you want to debug your probe interactively, try using something like p = garak._plugins.load_plugin("probes.mynewprobe.MyNewProbe") from a Python prompt to load the probe. The variable p will be assigned an instance of the probe (if instantiation was successful) and you can test a lot of the probe’s intended functionality from here.

Finally, check a few properties:

  • Does the new probe appear in python -m garak --list_probes?

  • Does the probe run? python -m garak -t test -p mynewprobe.MyNewProbe

  • Do the garak tests pass? python -m pytest tests/

Done!

Congratulations on writing a probe for garak!

If you’ve tested your probe and validated that it works, run black --config pyproject.toml <your updated files> to format your code in accordance with garak code standards. Once your code is properly tested and formatted, push your work to your github fork and open a pull request – thanks for your contribution!