Q: How can I tell if my Mac has been hacked.

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:

          Mac OS X Snow Leopard and malware detection

          OS X Lion- Protect your Mac from malware

          OS X Mountain Lion- Protect your Mac from malware

          About file quarantine in OS X

If you require anti-virus protection Thomas Reed recommends using Dr.Web Light from the App Store. It's free, and since it's from the App Store, it won't destabilize the system. If you prefer one of the better known commercial products, then Thomas recommends using Sophos.(Thank you to Thomas Reed for these recommendations.) If you already use Sophos, then be aware of this if you are using Mavericks: OS X Mavericks- Sophos Anti-Virus on-access scanner versions 8.0 - 9.1 may cause unexpected restarts

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.

What makes you think this?

Has it been out of your physical control for any time?

Allan

You can download "avast!" off of CNET. I personally think it works really well. All you need is to get a registration and press "Scan Entire System."

I think your hesitation is a good thing

Personally any time I see a Mac with problems if it has any AV software installed, I remove it. Usually my job is done after the AV software is removed.

AV software on a Mac seems to cause far more problem then it ever solves.

You are welcome

yes

How do I get rid of pop-ups that keep asking me for keychain passwords

You might want to consider starting a new discussion. Since this one is marked solved and a couple of years old, less people are likely to look at it. A new post would be much more visible. You can link to this one.

Keychain Issues - Resolve  see post by Kappy

OS X always asking to use your keychain passwords