Helpful Links Regarding Malware Protection
An excellent link to read is Tom Reed's Mac Malware Guide.
Also, visit The XLab FAQs and read Detecting and avoiding malware and spyware.
See these Apple articles:
From user Joe Bailey comes this equally useful advice:
The facts are:
1. There is no anti-malware software that can detect 100% of the malware out there.
2. There is no anti-malware that can detect anything targeting the Mac because there
is no Mac malware in the wild, and therefore, no "signatures" to detect.
3. The very best way to prevent the most attacks is for you as the user to be aware that
the most successful malware attacks rely on very sophisticated social engineering
techniques preying on human avarice, ****, and fear.
4. Internet popups saying the FBI, NSA, Microsoft, your ISP has detected malware on
your computer is intended to entice you to install their malware thinking it is a
protection against malware.
5. Some of the anti-malware products on the market are worse than the malware
from which they purport to protect you.
6. Be cautious where you go on the internet.
7. Only download anything from sites you know are safe.
8. Avoid links you receive in email, always be suspicious even if you get something
you think is from a friend, but you were not expecting.
9. If there is any question in your mind, then assume it is malware.
Marcel Brown's FBI “Ransomware” Phishing Scam Affects Mac Users – How To Bypass.
thomas_r.'s FBI ransomware “virus” rampant.
Start by trying to use the Safari back button ◀︎ to get away from that page.
If that doesn't work, force quit Safari and re-open Safari with the shift key held down.
Choose "Reset Safari..." from the Safari menu to clear the history and cache files of this page.
If you continue to have problems with being re-directed to adware, use the first two references that Kappy gave you.