1. A method for protecting client computers, comprising: receiving webpage data at a proxy from a webpage before the data reaches an intended recipient, the proxy is disposed as an intermediary between a server serving up the webpage and the intended recipient; gathering scripting-language-data from the webpage data; generating a parse tree from the gathered scripting-language-data; normalizing string-splitting constructs to reduce a level of string splitting in the parse tree; replacing variable names of the parse tree with standard names; generating a representation of at least a portion of the standard names; comparing the representation with signatures of known scripting language exploits; and preventing the scripting-language-data from reaching the intended recipient if the representation matches a signature of the one of the known scripting language exploits.