On April 3, CNBC reported the details of a large-scale attack campaign targeting the banking industry. As a result of this campaign, multiple U.S. banks experienced website outages totaling 249 hours over a six week period. Would the damage from the attack campaign have been reduced if the banks had the ability to share crowd-sourced threat intelligence? Imperva's Application Defense Center (ADC) recently analyzed real-world traffic from sixty Web applications to identify attack patterns. The results of the study demonstrate how sharing attack patterns across a community of Web applications can significantly mitigate the risk of large-scale attack campaigns. This presentation will: identify how cross-site information sharing (crowd-sourcing) creates security intelligence, demonstrate the value of adding crowd-sourced intelligence to Web application security, and provide real-world examples of attack patterns that can be shared for community defense.