Answer: The statement implies that the hackers psychologically manipulate the human to access the information they need.
Explanation: The author states that the hacker does not only exploits technology to get system access or to gather information. But there is another pivotal part of hacking. He refers to this part as "social engineering".
Social engineering from information security perspective means manipulate human emotions and convincing them to disclose some confidential information. Hacker often hacks or defrauds after gaining confidence and trust of a person.
Phishing is an example. It is a fraudulent technique for getting some secret information. Phisher sends an email pretending to be from some reputable organization to persuade people to divulge private information like passwords and credit card numbers, ATM card pin etc.
Answer:
In classification problems, the primary source for accuracy estimation is the confusion matrix (or classification matrix or contingency table)
Depends on what kind of goal.
If I gave a goal of eating 8 hot dogs then a barrier would be a physical will of your body to not eat more. It would be a limit your body can take so it’s different from a mental or other barrier.
If you wanted to cross an area of land but there is a fence in the way then that’s another type of barrier.
Or there are mental barriers. If you wanted to ask someone out to prom, you may be stopped by a mental barrier of self hatred. Feeling like you’re not good enough.
Hopefully this helps!
Data availability is the one related to the server being down.
