Understanding how to thwart click fraud via metrics alone is a complex and laborious task. Click fraud detection companies offer an affordable and effective option for marketers who want to initate auditing without having to understand all the mechanics behind it.

• WhosClickingWho.com - This fraud detector tracks all PPC search engines, detects multiple IP's. They also provide a deter feature that pops up a "ClickMinder" after suspected click abuse.
• ClickDetective - ClickDetective allows you to monitor click-throughs from all sources, detect and deter potential click fraud, and manage your campaigns. Real-time reporting is a standout feature.
• Clicklab - Clicklab provides PPC advertisers and publishers with managed click fraud detection, custom web analytics software, and professional services to help you increase online marketing ROI.
• Click Defense - Click Defense provide click fraud and web analytics services. Their systems utilize over 50 proprietary filters giving you true insight into your search engine visitor behavior.

Click fraud is an unfortunate side effect of PPC marketing, and wise marketers know that click fraud auditing is an important part of an overall PPC strategy.