Building Profanity Filters: clbuttic sh!t

BUILDING PROFANITY
FILTERS
clbuttic sh!t

Framework Days. IT Saturday. 5.09.2015
INTERNET CENSORSHIP
children
religion
sexual
https://en.wikipedia.org/wiki/Censorship

WHY FILTERING GOOD
ETHNICITY
PROTECTS
CHILDREN
RELIGION
SEXUAL ORIENTATION

WHY FILTERING BAD
lack of trust
to your users
their willing to
break rules
→

COCK

LET’S BUILD FILTER!
ﬁlter =
list of dirty words +
list of replacements +
ﬁlter rule

– George Carlin, 1972
Shit, piss, fuck, cunt, cocksucker,
motherfucker, and tits.
“Seven Words You Can Never Say
on Television”

FILTER RULES
1. search by entry
psss…

RANGE OF WORD
NSRange range = [text rangeOfString:badWord options:NSCaseInsensitiveSearch];
BOOL hasDirtyWord = [text localizedCaseInsensitiveContainsString:badWord];

RANGE OF WORD
- (NSArray * )rangesOfBadWordsWithSpaceInString:(NSString * )text {
__block NSMutableArray * result = [NSMutableArray array];
[self.listOfBadWordsWithSpace enumerateObjectsUsingBlock:^(NSString * badWord,
NSUInteger idx, BOOL * stop) {
NSRange range = [text rangeOfString:badWord options:NSCaseInsensitiveSearch];
while (range.location != NSNotFound) {
[result addObject:[NSValue valueWithRange:range]];
NSRange nextRange = NSMakeRange(range.location + 1, [text length] - range.location - 1);
range = [text rangeOfString:badWord
options:NSCaseInsensitiveSearch
range:nextRange];
}
}];
return result;
}

SEARCH BY ENTRY
Get your ass down here!The grass
around the creek was new, giving it a
velvety look. Dusty, his heartless
assassin, had found his mate.

FALSE POSITIVES

assart
assault
association
assurance
‘ASS’ WORDS
harassment
hassel
hourglass
impassable
pass
passion
piassaba
preassign
1250 words found
http://www.morewords.com/contains/ass/

ass → butt
REPLACEMENT RULES…

classic → clbuttic
…FAILS

Constitution →
Consbreastution
AND FAILS AGAIN…
medieval →
medireview
Tyson Gay →
Tyson Homosexual

FILTER RULES
1. search by entry
2. search whole word don’t u
know me?

SEARCH WHOLE WORD
NSString * scanned;
if ([scanner scanCharactersFromSet:wordCharacters intoString:&scanned]) {
if ([wordSet containsObject:[scanned lowercaseString]]) {
NSRange range = NSMakeRange(scanner.scanLocation - scanned.length, scanned.length);
[result addObject:[NSValue valueWithRange:range]];
}
}
NSSet * badWordsSet = [NSMutableSet setWithArray:self.listOfBadWords];
NSScanner * scanner = [NSScanner scannerWithString:text];
NSCharacterSet * wordCharacters = [NSCharacterSet alphanumericCharacterSet];

SEARCH WHOLE WORD

SPACE!
AND OTHER PUNCTUATION

Get your a s s down here!You'd
probably ﬁre my a.s.s the ﬁrst day on
the job. You've covered my a_s_s
every time I screwed up.
PUNCTUATION

FILTER RULES
1. search by entry
2. search whole word
3. handle punctuation
don’t tell
anyone…

1337 59341<

L33T SPEAK
HOW MANY DIFFERENT
SPELLINGS HAS ONE WORD?

BITCH

B1TCH
I → 1
BITCH

B!TCH
I → !
BITCH B1TCH

BI+CH
T → +
BITCH B1TCH B!TCH

I3ITCH
B → I3
BITCH B1TCH B!TCH BI+CH

BITCH
B!TCH
B1TCH
8ITCH
ßITCH
13ITCH
L3ITCH
BI7CH
BI+CH
BI†CH
BIT[H
BIT¢H
BIT<H
BITC#
BITC:
B1T¢H
8!†C#
8ITC/-/
817[#
(3][+(:

FILTER RULES
1. search by entry
4. handle l33t speak
my name
is…

SCUNTHORPE PROBLEM
https://en.wikipedia.org/wiki/Scunthorpe_problem

NICE TITS
In 2007, the Royal Society
for the Protection of Birds
blocked ornithological
terms such as cock (male
bird) and tit, shag and
booby from its discussion
forums

FILTER RULES
1. search by entry
4. handle l33t speak
5. remember about exceptions
blue-
footed booby!

TEXT FILTERING ON IOS
words dictionary
(boobs, b00bs,
b00b5)
whole word scan
NSScanner, NSSet

phrases dictionary
(b o o b s, b.o.o.b.s,
b!o!o!bs)
substring scan
rangeOfString

words dictionary
(boobs, b00bs,
b00b5)
whole word scan
NSScanner, NSSet
phrases dictionary
(b o o b s, b.o.o.b.s,
bo!obs)
substring scan
rangeOfString+

HOW FAST IS IT?
time,seconds
0
0,1
0,2
0,3
0,4
user text, characters count
1000 5000 10000 20000
range scanner both
dirty words
dictionary
contains 455
words

LIVE FILTERING
use RAC and run ﬁlter
every time user inputs
character

IMPROVE FILTERING
• Keep dictionary up to date
• Whitelist
• Levenshtein distance
• Soundex functions (where a word sounds like another)
• Naive bayesian inference ﬁltering of phrases/terms

POST-MODERATION
alive moderators
solid community
ﬂag abuse

DIRTY WORDS
• list of dirty words in different languages
https://github.com/shutterstock/List-of-Dirty-
Naughty-Obscene-and-Otherwise-Bad-Words
• list of dirty words i’ve used
https://gist.github.com/vixentael/
5ce4168e3e94d9686405

LAST SLIDE
@vixentael
iOS developer at Stanfy

THANK YOU
FOR WATCHING!

Building Profanity Filters: clbuttic sh!t

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