4. Development

You can easily add a new methods of detection if a packet is a spam or not. Simplest way is to implement a new filter.

4.1. Implementation of a new filter

Each class used as a filter by SpamProcessor needs to implement SpamFilter interface.

There are 3 important methods which need to be implemented by in SpamFilter interface:

• String getId() - returns id of a filter

• double getSpamProbability() - returns probability of sender being a spammer after detection of a single message which is blocked (from 0.0 to 1.0 where 1.0 means that it is a spammer)

• boolean filter(Packet packet, XMPPResourceConnection session) - method checking if a stanza is a spam (return false to stop stanza from being delivered)

Simple filter with id dummy-detector which would look for messages with text dummy, block them and then mark sender as a spammer after 5 messages would look like this:

Example filter.

package test;
import tigase.spam.SpamFilter;

@Bean(name = "dummy-detector", parent = SpamProcessor.class, active = true)
class DummyDetector implements SpamFilter {

    @Override
    public String getId() {
        return "dummy-detector";
    }

    @Override
    public double getSpamProbability() {
        return 0.2;
    }

    @Override
    protected boolean filterPacket(Packet packet, XMPPResourceConnection session) {
        if (packet.getElemName() == "message") {
            Element bodyEl = packet.getElement().getChild("body");
            if (bodyEl != null) {
                String body = bodyEl.getCData();
                if (body != null) {
                    return !body.contains("dummy");
                }
            }
        }
        return true;
    }
}

Note

If you expect packet to be processed multiple times (ie. by filter of a sender and filer of a received), then you should take that into account when you estimate value returned by getSpamProbability().

Tip

We have added @Bean annotation to automatically enable this filter in the SpamProcessor in the Tigase XMPP Server and to be able to easily configure it without specifying full name of a class.