Google's Webmaster Blog has recently posted about their #NoHacked campaign. This campaign is about giving website owners tips and tricks to ensure they don't fall victim to a cyber attack. You can read about the campaign here, I highly encourage you do -- it gives some great advice.
Part of the advice they gave was about using Google Alerts to notify you if there is any suspicious keywords on your website.
Using Google Alerts for this task is very simple. Simply go to Google Alerts and setup an alert similar to:
site:example.com "spammy keyword here"
Change 'example.com' to your domain, and change 'spammy keyword here' to the keyword you wish to be notified of, remember to leave the double quotes (").
Your alert should look similar to this: