This informative book provides an accessible overview of denial-of-service attacks, describing how and why this cyber threat happens and how people fight it. The book also includes a special feature focused on cyber safety, several informative sidebars, a table of contents, a reading comprehension quiz, a glossary, additional resources, and an index. This Focus Readers book is at the Navigator level, aligned to reading levels of grades 3–5 and interest levels of grades 4–7.