Hackers and network attacks

Hackers are people skilled at breaking into computer systems. They come in three 'hats':

• White hats (ethical hackers) find security flaws so they can be fixed, usually with the owner's permission.
• Black hats, also called crackers, exploit flaws for gain or to cause harm.
• Grey hats hack for the challenge, without bad intentions, but also without permission.

Network attacks:

• Denial of Service (DoS): the attacker floods a website or server with so many requests that real users cannot use it. In a Distributed DoS (DDoS), the flood comes from many computers at once: zombie computers infected with malware and controlled together as a botnet. So: one source means DoS; many zombies mean DDoS.
• Intrusion attacks try to get inside a network, using tricks such as asymmetric routing, buffer overflow (overloading a program's memory to make it run the attacker's code), and traffic flooding.
• Snooping (or sniffing) captures data travelling on a network, to analyse it later. Network administrators also use it legitimately, to troubleshoot.
• Eavesdropping intercepts private communication, such as calls or messages, as it happens, in real time. It used to be called wiretapping.