The glossary below contains many of the terms you will find in common use throughout our website. Please refer to this list to find definitions of terms and answers to other Internet security-related questions.


A worm is a type of non-parasitic malicious code that purposely replicates a possibly evolved copy of itself by exploiting security vulnerabilities on systems. The vulnerabilities that a worm exploits need not be exclusively software faults. It may also exploit configuration errors or operator errors. Unlike viruses, worms do not replicate by attaching themselves to a host executable or by modifying the system environment to execute the malicious code.