A PHP class to query the StopForumSpam web API or DNSBL for information about an IP address. Help protect your comments, contact form, or other user-generated content from spammers by checking the StopForumSpam database in real time.

SFSQuery is platform-agnostic and can be used with any project. Simply require() the class file or place it where your autoloader can find it; Composer installation is supported.

The simplest implementation uses an anonymous object to check whether or not an IP meets one of several criteria. For example, you might want to reject an action if the user's IP has been reported to StopForumSpam in the past 7 days:

<?php
use parseword\SFSQuery\SFSQuery;

if ((new SFSQuery($_SERVER['REMOTE_ADDR']))->wasReportedInPastDays(7)) {
    header('HTTP/1.1 403 Forbidden');
    echo "Sorry, you don't have access to this resource.";
    exit;
}
else {
    //Process the action
}

Because IP addresses frequently change hands, it's wise to use a more refined assessment based upon multiple factors. Just instantiate an SFSQuery object and call as many getter methods as you need. Let's check to see if an IP has been reported in the past 30 days, and has a spammer confidence level greater than 25%:

<?php
use parseword\SFSQuery\SFSQuery;

$sfs = new SFSQuery($_SERVER['REMOTE_ADDR']);
if ($sfs->wasReportedInPastDays(30) && $sfs->getConfidence() > 25) {
    //Reject the comment
    exit;
}
else {
    //Process the comment
}

Perhaps you want to reject IPs from Russia which have been reported to StopForumSpam more than 10 times:

<?php
use parseword\SFSQuery\SFSQuery;

$sfs = new SFSQuery($_SERVER['REMOTE_ADDR']);
if ($sfs->getFrequency() > 10 && $sfs->getCountry() == 'ru') {
    //Reject the comment
    exit;
}
else {
    //Process the comment
}

You should experiment to figure out what combination of factors is too "spammy" for your liking. You don't want to let a bunch of spammers through, but you don't want to cause a lot of false positives either. Consider a multi-tiered approach where high confidence spammers get rejected outright, lower scoring IPs have their comments flagged for moderator review, and totally clean IPs are free to submit content at will.

StopForumSpam offers several data points about each IP in their database. SFSQuery exposes them all through getter methods.

• getAppears() - Whether or not the IP is in the StopForumSpam database.

• getAsn() - The Autonomous System Number that announces the IP. (Web API only.)

• getConfidence() - A score from 0 to 100 calculated by StopForumSpam indicating how likely the IP is to be a spammer.

• getCountry() - Two-letter country code corresponding to the IP; reasonably accurate. (Web API only.)

• getFrequency() - How many times the IP has been reported to StopForumSpam.

• getLastSeen() - The epoch timestamp of the most recent time an IP was reported.

There are several additional methods available:

• setQueryMethod() - Switch from querying the web API (default) to the DNSBL, see next section.

• getApiResponse() - If an API query succeeds, this will contain the JSON reply from StopForumSpam.

• getDnsResponse() - If a DNSBL query succeeds, this will contain the A record or NXDOMAIN.

• getError() - If an error was encountered, this should tell you why.

• wasReportedInLastDays() - Whether or not the IP has been reported in the specified number of days.

• wasReportedSince() - Whether or not the IP has been reported since the given epoch timestamp.

To prevent unnecessary network traffic, the StopForumSpam API is queried only once during the lifetime of an SFSQuery object, with all of the data points being set during the initial query. If you use an object caching layer on top of PHP, consider forcing SFSQuery objects to be garbage collected at some regular interval so you aren't seeing stale results.

SFSQuery version 1.1.0 introduces the ability to query StopForumSpam's DNSBL service instead of the web API. Using the DNSBL offers several advantages:

• Requests are smaller, decreasing network traffic
• DNS typically uses UDP, eliminating TCP setup/teardown time
• Responses are cached by the DNS infrastructure, reducing load on StopForumSpam

The trade-off is that StopForumSpam's DNSBL doesn't provide information about the target IP's ASN or country code. The getAsn() and getCountry() methods aren't compatible with DNSBL mode and will return 0 and null, respectively.

To make SFSQuery use the DNSBL instead of the web API, you must instantiate an SFSQuery object and call setQueryMethod(SFSQuery::QUERYMETHOD_DNS);

<?php
use parseword\SFSQuery\SFSQuery;

$sfs = new SFSQuery($_SERVER['REMOTE_ADDR']);
$sfs->setQueryMethod(SFSQuery::QUERYMETHOD_DNS);

if ($sfs->wasReportedInPastDays(7) && $sfs->getConfidence() > 50) {
    //Reject the comment
    exit;
}
else {
    //Process the comment
}

Remember that if you use the DNSBL service, you won't be able to test for the IP's ASN or country code.

SFSQuery is written for PHP 7. To perform API connections, it requires one of the following to be available: fopen() URL wrappers, curl, or fsockopen(). To query the DNSBL, the gethostbyname() function must be available.

At present, only queries for IP addresses are supported. Web API queries can be made for both IPv4 and IPv6 addresses. DNSBL queries are currently limited to IPv4 addresses only. The ability to query email addresses may come in a future release.

The author is not affiliated with the StopForumSpam project. Any use of their service must comply with their Acceptable Use Policy.