capec

Common Attack Pattern Enumeration and Classification (CAPEC) effort is a publicly available, community-developed list of common attack patterns along with a comprehensive schema and classification taxonomy. Each attack pattern captures knowledge about how specific parts of an attack are designed and executed, providing the attacker's perspective on the problem and the solution, and gives guidance on ways to mitigate the attack's effectiveness.
The author looked at 453 documented attack patterns and enumerated the associated severity, likelihood of exploit and attacker skill required as documented by CAPEC, eventually identifying 27 attack patterns.

More information at http://capec.mitre.org/data/index.html#downloads