If the fans in people's computers started making a lot of noise I am sure they'd notice .... even without any antivirus software.
Not only that but CPU/GPU mining is horribly inefficient (using a computer to mine) when compared to what an ASIC can produce. For example a 1 TH ASIC will produce ~.014 BTC per day (or roughly $5.51 per day). By comparison your average laptop computer will be able to mine at a rate of ~20 kh/s. You would need 50 of these computers to mine at 1 mh/s. You would need 1,000 mh/s in order to equal one gh/s (so far you need 50,000 computers to mine 1 gh/s). You would need 1,000 gh/s in order to mine at a rate of 1 th/s. This works out to 50,000,000 computers that can mine at a rate of 20 kh/s each in order to make ~$5.50 per day. Do you really think this would be worth a hacker's time? I certainly do not
If it is not important for you,then it can be important for others here