Section: Software Development Security
Explanation

An issue with signature-based ID is that only attack signatures that are stored in their database are detected. New attacks without a signature would not be reported. They do require constant updates in order to maintain their effectiveness.
Reference used for this question: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 49

Worms can reproduce themselves without the help of system applications or resources.

An intranet is an Internet-like logical network that uses a firm's internal, physical network infrastructure. Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 99.