How would I know my fedora 21 have no spywares , virus and my privacy is protected?

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There are several layers of security in Fedora, see https://docs.fedoraproject.org/en-US/...

With that in mind, there can be several issues or concerns including bugs and vulnerabilities , for example poodle and shockshell

https://access.redhat.com/articles/12...

http://fedoramagazine.org/shellshock-...

http://fedoramagazine.org/shellshock-...

Your main lines of defense are:

1. Linux permissions - you should be running as a user , not as root.

2. Updates - As bugs/vulnerabilities are found, they are patched, so keep your system up to date.

3. selinux - selinux helps mitigate zero day exploits.

BUT you can have malicious code in your home directory such as browser hijacks. For this remove your files in $HOME

See https://ask.fedoraproject.org/en/ques...

Beyond those issues ....

1. Use safe browsing. You can run browsers in a selinux sandbox if you wish (install sandbox if needed)

   sudo dnf install policycoreutils-sandbox

Then

sandbox -X -H sehome -T tmp -t sandbox_web_t firefox

Adjust your browser as needed ;)

See also http://danwalsh.livejournal.com/28545... and https://www.linux.com/learn/tutorials...

To know if you have malware you need to do some sort of penetration testing. Pentesting is a large topic but you can do some basics

1. rpm will confirm system files, but you sort of need to know what a fresh install looks like as the is a large output evein on a fresh install

http://www.sans.org/security-resource... and http://www.rpm.org/max-rpm/s1-rpm-ver...

1. HIDS - OSEC or similar - http://www.ossec.net/

2. Antivirus - Antivirus for linux exists, but again often throws false positives.

3. rootkits - these can be very difficult to detect. there is a program, rkhunter, but as with antivirus, you get more false positives then true positives. See http://www.tecmint.com/install-linux-... and also https://ask.fedoraproject.org/en/ques...

I can not stress enough, you really need to be familiar with all of the tools you wish to use and what a "normal" system looks like BEFORE you go looking for problems.

After all that you are left with forensics

See www.blackhat.com/presentations/bh-usa...

There is a Fedora security spin and you will need to make extensive use of google or obtain training/education.

Privacy is also a broad issue, sort of depends on what you mean by privacy.

1. First line - give each user a unique home.

2. If guests use your machine, use xguest.

3. Internet privacy is , IMO, very much an illusion as "the internet" is public. Take a look at

http://bodhizazen.net/Tutorials/Privacy

and the TOR documentation https://www.torproject.org/docs/faq.h...

rm -rf $HOME/.cache/sessions/*

Please first read these similar Questions - Answers

1) https://ask.fedoraproject.org/en/ques...

2) https://ask.fedoraproject.org/en/ques...

If you have a problem with Firefox, try to reset Firefox from About → Troubleshooting Information → Refresh Firefox.

Also check the StartUp Applications in the KDE Session and uncheck any unusual entry there.

Especially in Fedora you are protected twice because of SELinux.