Imperva (http://www.imperva.com ) isolated the four most prevalent Web application attacks:
1. Directory traversal = 37% 2. cross site scripting =36% 3. SQL injection =23% 4. Remote file include =4%
Sources:- http://www.imperva.com/index.html http://www.pcmag.com/article2/0,2817,2389117,00.asp