Hacking can refer to authorized or unauthorized attempts to bypass security mechanisms. A hacker is someone who takes advantage of security weaknesses in a system. There are different types of hackers - white hat hackers help identify weaknesses, black hat hackers break into systems to steal information or cause damage, and grey hat hackers fall between white and black hats. Ethical hacking involves company engineers hacking their own systems to improve security. Famous hackers include Stephen Wozniak, Tsutomu Shimomura, Kevin Mitnick, and Kevin Poulsen. Social media sites are a common target for hacking. Installing antivirus software, avoiding personal information disclosure, and frequent scans can help prevent hacking.