rustrict

rustrict is a profanity filter for Rust.

^{Disclaimer: Multiple source files (.txt, .csv, .rs test cases) contain profanity. Viewer discretion is advised.}

Features

• Multiple types (profane, offensive, sexual, mean, spam)
• Multiple levels (mild, moderate, severe)
• Resistant to evasion
  • Alternative spellings (like "fck")
  • Repeated characters (like "craaaap")
  • Confusable characters (like 'ᑭ', '𝕡', and '🅿')
  • Spacing (like "c r_a-p")
  • Accents (like "pÓöp")
  • Bidirectional Unicode (related reading)
  • Self-censoring (like "f*ck")
  • Safe phrase list for known bad actors]
  • Censors invalid Unicode characters
  • Battle-tested in Mk48.io
• Resistant to false positives
  • One word (like "assassin")
  • Two words (like "push it")
• Flexible
  • Censor and/or analyze
  • Input &str or Iterator<Item = char>
  • Can track per-user state with context feature
  • Can add words with the customize feature
  • Accurately reports the width of Unicode via the width feature
  • Plenty of options
• Performant
  • O(n) analysis and censoring
  • No regex (uses custom trie)
  • 3 MB/s in release mode
  • 100 KB/s in debug mode

Limitations

• Mostly English/emoji
• Censoring removes most diacritics (accents)
• Does not detect right-to-left profanity while analyzing, so...
• Censoring forces Unicode to be left-to-right
• Doesn't understand context
• Not resistant to false positives affecting profanities added at runtime

Usage

Strings (&str)

use rustrict::CensorStr;

let censored: String = "hello crap".censor();
let inappropriate: bool = "f u c k".is_inappropriate();

assert_eq!(censored, "hello c***");
assert!(inappropriate);

Iterators (Iterator<Type = char>)

use rustrict::CensorIter;

let censored: String = "hello crap".chars().censor().collect();

assert_eq!(censored, "hello c***");

Advanced

By constructing a Censor, one can avoid scanning text multiple times to get a censored String and/or answer multiple is queries. This also opens up more customization options (defaults are below).

use rustrict::{Censor, Type};

let (censored, analysis) = Censor::from_str("123 Crap")
    .with_censor_threshold(Type::INAPPROPRIATE)
    .with_censor_first_character_threshold(Type::OFFENSIVE & Type::SEVERE)
    .with_ignore_false_positives(false)
    .with_ignore_self_censoring(false)
    .with_censor_replacement('*')
    .censor_and_analyze();

assert_eq!(censored, "123 C***");
assert!(analysis.is(Type::INAPPROPRIATE));
assert!(analysis.isnt(Type::PROFANE & Type::SEVERE | Type::SEXUAL));

If you cannot afford to let anything slip though, or have reason to believe a particular user is trying to evade the filter, you can check if their input matches a short list of safe strings:

use rustrict::{CensorStr, Type};

// Figure out if a user is trying to evade the filter.
assert!("pron".is(Type::EVASIVE));
assert!("porn".isnt(Type::EVASIVE));

// Only let safe messages through.
assert!("Hello there!".is(Type::SAFE));
assert!("nice work.".is(Type::SAFE));
assert!("yes".is(Type::SAFE));
assert!("NVM".is(Type::SAFE));
assert!("gtg".is(Type::SAFE));
assert!("not a common phrase".isnt(Type::SAFE));

If you want to add custom profanities or safe words, enable the customize feature.

#[cfg(feature = "customize")]
{
    use rustrict::{add_word, CensorStr, Type};

    // You must take care not to call these when the crate is being
    // used in any other way (to avoid concurrent mutation).
    unsafe {
        add_word("reallyreallybadword", (Type::PROFANE & Type::SEVERE) | Type::MEAN);
        add_word("mybrandname", Type::SAFE);
    }
    
    assert!("Reallllllyreallllllybaaaadword".is(Type::PROFANE));
    assert!("MyBrandName".is(Type::SAFE));
}

But wait, there's more! If your use-case is chat moderation, and you can store data on a per-user basis, you might benefit from the context feature.

#[cfg(feature = "context")]
{
    use rustrict::{BlockReason, Context};
    use std::time::Duration;
    
    pub struct User {
        context: Context,
    }
    
    let mut bob = User {
        context: Context::default()
    };
    
    // Ok messages go right through.
    assert_eq!(bob.context.process(String::from("hello")), Ok(String::from("hello")));
    
    // Bad words are censored.
    assert_eq!(bob.context.process(String::from("crap")), Ok(String::from("c***")));

    // Can take user reports (After many reports or inappropriate messages,
    // will only let known safe messages through.)
    for _ in 0..5 {
        bob.context.report();
    }
   
    // If many bad words are used or reports are made, the first letter of
    // future bad words starts getting censored too.
    assert_eq!(bob.context.process(String::from("crap")), Ok(String::from("****")));
    
    // Can manually mute.
    bob.context.mute_for(Duration::from_secs(2));
    assert!(matches!(bob.context.process(String::from("anything")), Err(BlockReason::Muted(_))));
}

Comparison

To compare filters, the first 100,000 items of this list is used as a dataset. Positive accuracy is the percentage of profanity detected as profanity. Negative accuracy is the percentage of clean text detected as clean.

Crate	Accuracy	Positive Accuracy	Negative Accuracy	Time
rustrict	79.81%	93.99%	76.27%	9s
censor	76.16%	72.76%	77.01%	23s

Development

If you make an adjustment that would affect false positives, such as adding profanity, you will need to run false_positive_finder:

1. Run make downloads to download the required word lists and dictionaries
2. Run make false_positives to automatically find false positives

If you modify replacements_extra.csv, run make replacements to rebuild replacements.csv.

Finally, run make test for a full test or make test_debug for a fast test.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.