I am trying to prevent certain kinds of posts on my site, which are mostly meant to make it look like they contain some content but are just spam. Specifically, the posts are a few random words, some newline characters, and a random character.
So, I know some legit users might have use for using two newline chars (to create a blank line between paragraphs), but I figure 3+ can be marked as spam.
I tested this regex on regex101 and it works fine, but is never triggered when I test on my site, any ideas as to why? When I uncomment the echo line, it will show me the number 4 for my test data, so I know it sees the newlines.. is my regex formed incorrectly?!
Test data:
This is a potential
spam post
Code:
//echo substr_count($lowercaseBody, "\n");
if (preg_match('/\n{3,}./', $lowercaseBody)){
error("Stop Spamming my chan you .");
}
The data likely contains CRLF's, not just LF's.
The substr_count test does not care about the interleaving CR's, but your regex patterns does.
Use (\r?\n) instead of the \n to allow both CRLF's and LF's (different browsers/OS's, may use different new-lines):
if (preg_match('/(\r?\n){3,}./', $lowercaseBody)){
error("Stop Spamming my chan you .");
}
Assume "xyza" is a bad word. I'm using following method to replace offensive words-
$text = str_replace("x***","(Offensive words detected & removed!)",$text);
This code will replace xyza into "(Offensive words detected & removed!)".
But problem is "Case" if someone type XYZA my code can't detect it. How to solve it?
No matter what you do, users will find ways to get around your filters. They will use unicode characters (аss, for example, uses a Cyrillic а and will not get captured by any of the regex solutions). They will use spaces, dollar signs, asterisks, whatever you haven't managed to catch yet.
If family-friendliness is essential to your application, have a person review the content before it goes live. Otherwise, add a flag feature so other people can flag offensive content. Better yet, use some sort of machine learning or Bayesian filter to automatically flag potentially offensive posts and have humans check them out manually. People read human languages better than computers.
The problem with whitelists/blacklists is—as other users have pointed out—your users will make it their priority to find ways around your filter for satisfaction rather than using your website for what it was intended for, whatever that may be.
One approach would be to use Google’s undocumented profanity API it created for its “What Do You Love?” website. If you get a response of true then just give the user a message saying their post couldn’t be submitted due to detected profanity.
You could approach this as follows:
<?php
if (isset($_POST['submit'])) {
$result = json_decode(file_get_contents(sprintf('http://www.wdyl.com/profanity?q=%s', urlencode($_POST['comments']))));
if ($result->response == true) {
// profanity detected
}
else {
// save comments to database as normal
}
}
Other answers and comments say that programming is not the best solution to this problem. I agree with them. Those answers should be moved to Moderators - Stack Exchange or Webmasters - Stack Exchange.
Since this is stackoverflow, my answer is going to be based on computer programming.
If you want to use str_replace, do something like this.
For the sake of this post, since some people are offended by actual cusswords, let's pretend that these are bad words:
'fug', 'schnitt', 'dam'.
$text = str_ireplace(" fug ","(Offensive words detected & removed!)",$text);
Notice, it's str_ireplace not str_replace. The i is for "case insensitive".
But that will erroneously match "fuggedaboudit," for example.
If you want to do a more reliable job, you need to use regex.
$bad_text = "Fug dis schnitt, because a schnitter never dam wins a fuggin schnitting darn";
$hit_words = array("fug","schnitt","dam"); // these words are 'hits' that we need to replace. hit words...
array_walk($hit_words, function(&$value, $key) { // this prepares the regex, requires PHP 5.3+ I think.
$value = '~\b' . preg_quote( $value ,'~') . '\b~i'; // \b means word boundary, like space, line-break, period, dash, and many others. Prevends "refudgee" from being matched when searching for "fudge"
});
/*print_r($bad_words);*/
$good_words = array("fudge","shoot","dang");
$good_text = preg_replace($hit_words,$good_words,$bad_text); // does all search/replace actions at once
echo '<br />' . $good_text . '<br />';
That will do all your search/replacements at once. The two arrays should contain the same number of elements, matching up searches and replace terms. It will not match parts of words, only whole words. And of course, determined cussers will find ways of getting their swearing onto your website. But it will stop lazy cussers.
I've decided to add some links to sites that obviously use programming to do a first run through removing profanity. I'll add more as I come across them. Other than yahoo:
1.) Dell.com - replace matching words with <profanity deleted>.
http://en.community.dell.com/support-forums/peripherals/f/3529/t/19502072.aspx
2.) Watson, the supercomputer, apparently developed a cursing problem. How do you tell the difference between cursing and slang? Apparently, it's so hard that the researchers just decided to purge it all. But they could have just used a list of curse words ( exact matching is a subset of regex, I would say) and forbidden their use. That's kind of how it works in real life, anyway.
Watson develops a profanity problem
3.) Content Compliance section of Gmail custom settings in Apps for Business:
Add expressions that describe the content you want to search for in each message
The "Expresssions" used can be of several types, including "Advanced content match", which, among other things, allows you to choose "Match type" options very similar to what you'd have in an excel filter: Starts with, Ends with, Contains, Not contains, Equals, Is Empty, all of which presumably use Regex. But wait, there's more: Matches regex, Not matches regex, Matches any word, Matches all words. So, the mighty Google implements regex filtering options for its business users. Why would it do that, when regex is supposedly so ineffective? Because it actually is effective enough. It is a simple, fast, programming solution that will only fail when people are hell-bent on circumventing it.
Besides that list, I wonder if anyone else has noticed the similarity between weeding out profanity and filtering out spam. Clearly, regex has uses in both arenas but nitpickers who learned by rote that "all regex is bad" will always downvote any answer to any question if regex is even mentioned.
Try googling "how spam filters work". You'll get results like this one that covers spam assassin:
http://www.seas.upenn.edu/cets/answers/spamblock-filter.html
Another example where I'm sure regex is used is when communicating via Amazon.com's Amazon Marketplace. You receive emails at your usual email address. So, naturally, when responding to a seller, your email program will include all kinds of sender information, like your email address, cc email addresses, and any you enter into the body. But Amazon.com strips these out "for your protection." Can I find a way around this regex? Probably, but it would take more trouble than it's worth and is therefore effective to a degree. They also keep the emails for 2 years, presumably so that a human can go over them in case of any fraud claims.
SpamAssassin also looks at the subject and body of the message for the same sort of things that a person notices when a message "looks like spam". It searches for strings like "viagra", "buy now", "lowest prices", "click here", etc. It also looks for flashy HTML such as large fonts, blinking text, bright colors, etc.
Regex is not mentioned, but I'm sure it's in use.
Use str_ireplace function that Case-insensitive version of str_replace()
$text = str_ireplace("flip","(Offensive words detected & removed!)", $text);
Use 'str_ireplace' to replace any case sensitive strings
Probable, this will help you
$text = 'contains offensive_word .... so on';
$array = array(
'offensive_word' => '****',
'offensive_word2' => '****',
'offensive_word3' => '****',
//.....
);
$text = str_ireplace(array_keys($array),array_values($array), $text);
echo $text;
You should use regex replacement and need to add the i flag to the end of your regex so it searches your text regardless of case. so..
$text = preg_replace("/xyza/i","(Offensive words detected & removed!)", $text);
str_ireplace can also be used if you don't need complex regex rules.
$text = str_ireplace("xyza","(Offensive words detected & removed!)", $text);
In fact, the latter is the preferred way as it's faster than regex manipulation. From PHP docs:
If you don't need fancy replacing rules, you should generally use this function instead of preg_replace() with the i modifier.
BUT, as the commenter pointed out, simple string/regex replacements can break your strings if the substring you're replacing appears as part of another non-offensive word. For this, you could either use word boundaries in your regexes or replace only those words that can't be part of other strings (e.g. the word xyza).
Here's the skinny. I'm using imap to get into Gmail, and using that for database entries. I'm having quite the headache of it to. The main issue is that I'm getting all sorts of random '=''s in my body. I can get around most of it, but the headache comes from primarily one source. I'm isolating out JUST the reply, and the email body is similar to this.
<div dir="ltr">Quick Quick! He's Drowning!!!!!!</div><div class="gm=
ail_extra"><br clear="all"><div>Thank you<div>Daniel Jenkins</div><div>Te=
chnical Assistant</div><div><a href="[url]" target="_blank">=
[work]</a><br>
</div><div>[phone number here]</div></div>
<br><br>
Now, I don't need the email signature, I just need the part before it. What I'm trying to do is strpos the <div class="gmail_ extra line, but it's a moving target because of the =. It's been after the a, the l, the g, etc. Is there a way to strpos(<div calss=g[=]?m[=]?a[=]?i[=]?l[=]?)?
The ending = is a soft return / newline in quoted-printable encoding, just use:
$string = quoted_printable_decode($string);
... which will also take care of other unexpected differences between encoded body & actual content. After that you should have nice predictable HTML (which you would run through a parser rather then trying to split it with a regex).
I have a custom markup parsing function that has been working very well for many years. I recently discovered a bug that I hadn't noticed before and I haven't been able to fix it. If anyone can help me with this that'd be awesome. So I have a custom built forum and text based MMORPG and every input is sanitized and parsed for bbcode like markup. It'll also parse out URL's and make them into legit links that go to an exit page with a disclaimer that you're leaving the site... So the issue that I'm having is that when I user posts multiple URL's in a text box (let's say \n delimited) it'll only convert every other URL into a link. Here's the parser for URL's:
$markup = preg_replace("/(^|[^=\"\/])\b((\w+:\/\/|www\.)[^\s<]+)" . "((\W+|\b)([\s<]|$))/ei", '"$1".shortURL("$2")."$4"', $markup);
As you can see it calls a PHP function, but that's not the issue here. Then entire text block is passed into this preg_replace at the same time rather than line by line or any other means.
If there's a simpler way of writing this preg_replace, please let me know
If you can figure out why this is only parsing every other URL, that's my ultimate goal here
Example INPUT:
http://skylnk.co/tRRTnb
http://skylnk.co/hkIJBT
http://skylnk.co/vUMGQo
http://skylnk.co/USOLfW
http://skylnk.co/BPlaJl
http://skylnk.co/tqcPbL
http://skylnk.co/jJTjRs
http://skylnk.co/itmhJs
http://skylnk.co/llUBAR
http://skylnk.co/XDJZxD
Example OUTPUT:
http://skylnk.co/tRRTnb
<br>http://skylnk.co/hkIJBT
<br>http://skylnk.co/vUMGQo
<br>http://skylnk.co/USOLfW
<br>http://skylnk.co/BPlaJl
<br>http://skylnk.co/tqcPbL
<br>http://skylnk.co/jJTjRs
<br>http://skylnk.co/itmhJs
<br>http://skylnk.co/llUBAR
<br>http://skylnk.co/XDJZxD
<br>
e flag in preg_replace is deprecated. You can use preg_replace_callback to access the same functionality.
i flag is useless here, since \w already matches both upper case and lower case, and there is no backreference in your pattern.
I set m flag, which makes the ^ and $ matches the beginning and the end of a line, rather than the beginning and the end of the entire string. This should fix your weird problem of matching every other line.
I also make some of the groups non-capturing (?:pattern) - since the bigger capturing groups have captured the text already.
The code below is not tested. I only tested the regex on regex tester.
preg_replace_callback(
"/(^|[^=\"\/])\b((?:\w+:\/\/|www\.)[^\s<]+)((?:\W+|\b)(?:[\s<]|$))/m",
function ($m) {
return "$m[1]".shortURL($m[2])."$m[3]";
},
$markup
);
I have the following part of a validation script:
$invalidEmailError .= "<br/>» You did not enter a valid E-mail address";
$match = "/\b[A-Z0-9._%+-]+#[A-Z0-9.-]+\.[A-Z]{2,4}\b/";
That's the expression, here is the validation:
if ( !(preg_match($match,$email)) ) {
$errors .= $invalidEmailError; // checks validity of email
}
I think that's enough info, let me know if more is needed.
Basically, what happens is the message "You did not enter a valid E-mail address" gets echoed no matter what. Whether a correct email address or an incorrect email address is entered.
Does anyone have any idea or a clue as to why?
EDIT: I'm running this on localhost (using Apache), could that be the reason as to why the preg_match ain't working?
Thanks!
Amit
Your regex only includes [A-Z], not [a-z]. Try
$match = "/\b[A-Z0-9._%+-]+#[A-Z0-9.-]+\.[A-Z]{2,4}\b/i";
to make the regex case-insensitive.
You can test this live on http://regexpal.com.
However, I'd advise you to try one of the expressions on the page mentioned by strager: http://fightingforalostcause.net/misc/2006/compare-email-regex.php. They have been perfected over time and will probably behave better. But Gmail users will be satisfied with yours, since they'll be able to use plus aliases which are rejected incorrectly by many validators.
You likely got the regular expression you're using from regular-expressions.info. On that page, the author states (emphasis added):
If you want to use the regular expression above, there's two things you need to understand. First, long regexes make it difficult to nicely format paragraphs. So I didn't include a-z in any of the three character classes. This regex is intended to be used with your regex engine's "case insensitive" option turned on. (You'd be surprised how many "bug" reports I get about that.) Second, the above regex is delimited with word boundaries, which makes it suitable for extracting email addresses from files or larger blocks of text. If you want to check whether the user typed in a valid email address, replace the word boundaries with start-of-string and end-of-string anchors, like this: ^[A-Z0-9._%+-]+#[A-Z0-9.-]+.[A-Z]{2,4}$.
To solve this problem, add the i PCRE flag after your regular expression.
You can always try debugging your regex using a simpler tool (I'm quite fond of using Notepad++ for this purpose) and performing iterative tests - ie. making the expression more/less complicated and seeing if that fixes/breaks things.