There are different types of hackers - white hat hackers test security systems for vulnerabilities but do not have malicious intent, while black hat or cracker hackers break into systems to steal data or cause harm. Common hacking attacks mentioned include phishing, brute force attacks, cookie stealing, and email hacking by exploiting vulnerabilities or creating viruses and worms. An anti-virus program is created to detect and remove viruses from a system. A worm is a self-replicating virus that spreads to other computers without user intervention.