Provided are an apparatus, a system and a method for detecting and preventing malicious scripts. The apparatus for detecting and preventing malicious scripts includes a signature management unit managing a first signature including code pattern information of previously-detected malicious scripts, a script analysis unit receiving the first signature from the signature management unit and analyzing a first script, which is included in a web page, using the first signature, and a script processing unit receiving analysis result data from the script analysis unit and processing the first script according to the analysis result data.