Yes, you should.
That usually means an app or process or the system is busy. It helps to know what's running at the time. To get a picture of what's running:
- Launch Activity Monitor
- Change "My Processes" at the top to "All Processes"
- Click on the CPU column heading once or twice, so the arrow points downward (highest values on top).
- Click on the System Memory tab at the bottom.
- Take a screen shot of the entire Activity Monitor window, then scroll down to see the rest of the list, take another screen shot
- Post your screenshots.
No, you don't. Macs are not immune to malware, but no true viruses exist in the wild that can run on Mac OS X, and there never have been any since it was released over 10 years ago. The only malware in the wild that can affect Mac OS X is a handful of trojans, which can be easily avoided by practicing safe computing (see below). Also, Mac OS X 10.6 and later versions have
anti-malware protection built in, further reducing the need for 3rd party antivirus apps.
- Make sure your built-in Mac firewall is enabled in System Preferences > Security > Firewall
- Uncheck "Open "safe" files after downloading" in Safari > Preferences > General
- Disable Java in your browser (Safari, Chrome, Firefox). This will protect you from malware that exploits Java in your browser, including the recent Flashback trojan. Leave Java disabled until you visit a trusted site that requires it, then re-enable only for the duration of your visit to that site. (This is not to be confused with JavaScript, which you should leave enabled.)
- Change your DNS servers to OpenDNS servers by reading this.
- Be careful to only install software from trusted, reputable sites. Never install pirated software. If you're not sure about an app, ask in this forum before installing.
- Never let someone else have access to install anything on your Mac.
- Don't open files that you receive from unknown or untrusted sources.
- For added security, make sure all network, email, financial and other important passwords are long and complex, including upper and lower case letters, numbers and special characters.
- Always keep your Mac and application software updated. Use Software Update for your Mac software. For other software, it's safer to get updates from the developer's site or from the menu item "Check for updates", rather than installing from any notification window that pops up while you're surfing the web.
That's all you need to do to keep your Mac completely free of any Mac OS X malware that has ever been released into the wild.
While you may elect to use it, 3rd party antivirus software is not required to keep your Mac malware-free.
If you're having performance issues, this may help: