While dissecting the techniques that users desperately need for hacker defense, this book uses simple terms to provide readers a systematic knowledge of cybersecurity techniques, and teaches them to do better in guarding against hacker attack. The book is divided into the following 17 chapters: introduction to computer security; system vulnerability and security; system intrusion and remote control; protection against Trojans; protection against viruses; ultimate protection of system security; protection of file passwords; protection of disk data; protection of system account data; protection of social-media accounts and passwords; protection of web browsers; protection of mobile phones; protection of tablets; protection of online banking services; protection of mobile wallets; protection of Bluetooth devices; and protection of wireless network security.