Actively monitoring the percentage of XSS errors over time can determine patterns of when hackers attempt to gain access to a website's source code, database links, pricing and e-commerce systems. This is one of the most often used metrics in security dashboards used for monitoring Web-based applications and multisite installations. (%) Incidence and Trending of Buffer Overflow Injection Flaws -- This is most commonly associated with attempts to gain access to SQL databases supporting a website by forcing a buffer overflow condition (Brodkin, 2007). This is one of the most effective hacking strategies there are as it forces a system to fail and allow access.

(%) Authentication Soft and Hard Errors -- the most ubiquitous of metrics, this measures how many times passwords work or fail, and how their reset trending indicates that an automated set of code or a bot is attempting to gain literally hundreds of passwords for a system simultaneously (Brodkin, 2007).

(%) Service Level Agreement (SLA) hard security faults on system performance -- All services...

This metric, % of SLA hard security faults tells the percentage of time a given hard fault was encountered to the configuration management system for the website or complex or servers. A hard fault would be an attempt to either use XML or FTP to gain cross-channel access to servers and disrupt the site or bring it down. This is a technique used in more advanced Ddos attacks, which is specifically aimed at bringing down an entire site configuration.
References

Brodkin, J.. (2007, October). The top 10 reasons Web sites get hacked. Network World, 24(39), 1,16-17,20.

Su, M., Yu, G., & Lin, C.. (2009). A real-time network intrusion detection system for large-scale attacks based on an incremental mining approach. Computers & Security, 28(5), 301.

Xiong, K., & Perros, H. (2008). Trustworthy Web services provisioning for differentiated customer services.…