script kiddie

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A person who uses existing scripts, code, or other tools illicitly to gain entry to a computer system or network, without understanding the way the tools function or the way the system or network is designed.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun derogatory A (usually amateur) hacker who compromises files on others' computers or launches attacks on computer systems, using widely distributed computer programs or scripts, rather than using their own unique programs or scripts.