• Anti-Virus Program (Open the program and look for a way to update the product.  Renew the protection before it expires.)
• Anti-Malware Program (i.e. Malwarebytes' Anti-Malware a free program if you have it, but which doesn't update itself normally.)
• Windows (An indicator may be in the clock tray, but if not, Start > Control Panel > Windows Updates. [Vista & 7])
• Adobe Reader (Open Adobe Reader and check the Tools menu for an Update choice.)
• Adobe Flash (You may need to visit adobe.com and look for Adobe Flash on the right.  Download and install.)
• Java (Usually an orange icon in the clock tray.  Click it open to start the download.  Click it later to install.)

Most Anti-Virus programs update themselves, but it's a good idea to check the status by first opening the application's main panel, get updates when necessary and then do a monthly scan.  I usually check the quarantine or vault if I can find it.

Malwarebytes' Anti-Malware is a good program, but because it doesn't update itself, you need to click the update tab on the main panel of the program and get them first.  Then do a monthly Quick Scan and remove what it finds.

Windows updates come in from Microsoft on "Patch Tuesday" which is the 2nd Tuesday of the month late in the day.  For those using Windows XP, open Internet Explorer and from the Tools menu select Windows Updates.

Adobe Reader and Java usually have indicator icons in the clock tray which makes the updates easy to get.  Sometimes more than one update is available in a one-month period.  Since virus writers are targeting applications, these updates should be done regularly.

Updates for Apple Computers are usually easy to do, but they require that you know the administrator username and password.  You need them because technically you are making changes to the computer's operating system that requires elevated privileges.  Be aware that updates sometimes involve large downloads, so be prepared to leave your computer on and connected to the Internet.

To get started, here's list from http://www.apple.com/softwareupdate/:

1. Select Software Update from the Apple menu.
2. Click Update Now.
3. Choose the items you want to install (usually all of them), then click Install.
4. Enter your administrator username and password.
5. Next when all is done, restart the computer to use the revised system.
6. Finally select Software Update again because some updates may have required ones you just installed.

Since Software Update does not show updates available for apps that were purchased from the Mac App Store, open App Store on your Apple computer, and click the "Updates" view at the top of the App Store window. This will show all available updates for apps currently installed.

My recommendation: get updates once a month.

The good news comes in two kinds: 1. you don't need to do this very often, 2. it's really easy to do.  (I don't have any bad news on this.)  I recommend that you close up all other applications that may have been running before installing updates.  If the computer has been running for more than 24 hours, I would suggest a restart first.

Go to System > Administration > Update Manager and click the Check button.  After finding out what your computer needs and listing the items, click Install Updates.  The application will request the adminstrator password to change operating system files and settings and then it just gets on with it downloading and installing the updates.

At the end of the process you may be asked to restart the computer when it's appropriate for you to do so because an update might have installed an updated Linux kernel for the operating system that needs to be used.  New kernels have patches fixing vulnerabilities and an odd assortment of bugs along with additional or newer drivers for sound, video, printers, etc.

Generally an anti-virus program isn't needed for Ubuntu, though I use Clam Anti-Virus because users of Windows and Apple computers send me e-mail with attachments.  I don't want my computer to send malware on to other users even if it doesn't affect my own computer.