Why does a software installation window appear just before shutdown?

Try running this program and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor. Please use copy and paste as screen shots can be hard to read.

Etrecheck – System Information

That's from the Genieo adware. You can follow Apple's manual instructions for removing adware.

It should be noted that Apple's manual removal instructions are typically outdated. Sometimes a lot outdated. It depends on when Apple last updated their instructions page. You can find much more up-to-date instructions on The Safe Mac's adware removal page.

Why are you not listening to the advice given by Eric Root and Kurt Lang? Their advice would have solved your issue immediately and you wouldn't have to download useless virus software.

You do not have a virus, but you may have some adware that virus software is not going to get rid of

Installing antivirus software is not necessary or needed with OS X and will only make your problems worse as antivirus software running on OS X will negatively affect the normal operation of OS X.

You have gotten great advice from both Eric Root and Kurt Lang, I strongly suggest that you follow it before you do more damage to your Mac's system software.

As mentioned above, AV software is, and will be useless. You installed adware along with something else you recently installed. In this case, it's Genieo.

Currently for OS X 10.6.8 Snow Leopard, up to date FireFox is more secure than Safari.

It's not an issue with the web browser per say, but what sites you visit on those web browsers that can cause you to get adware/malware.

Antivirus software is NOT needed if the Mac you are running is only running OS X. Antivirus apps interfere with normal performance and operation of a Mac because they program too many controls (program extensions) into the main OS X system software impacting/impeding general performance of a Mac.

Here are some of my tidbits of advice on how to avoid viruses/adware/malware in the future, if you encounter adware/malware, again.

Some anti-virus solutions can slow down your Mac, but to be honest, the best anit-virus app is you, the user and your brain.

Don't visit questionable websites or website you are unsure about.

Don't use Torrents or engage in "Torrenting"

Don't install pirated software or software downloaded from a questionable or unknown websites or untrutsted sources.

Java is still a vulnerability concern, if you do not need it, don't use it.

Use a browser filter and pop-up blocker

Don't open email attachments from email addresses that you do not recognize.

Install security updates when they become available

Educate yourself as to what threats are common and active.

In effect, use your own brain as the antivirus filter.

Follow that advise and in MOST cases, you will be fine and won't risk your Mac to potential Trojans, malware or viruses.

If you feel you need some baseline virus protection that is minimally invasive on the Mac OS X system, install

ClamXAV

http://www.clamxav.com/

As mentioned, that "shut down" dialogue box is caused by Genieo. You'll continue to see it until you follow the instructions to remove Genieo in either of my links above.

Make sure to follow the removal instructions for Genieo in particular to the letter. Don't skip any steps. Where it says to restart the Mac after doing certain proceeding steps, do it.

The Genieo removal page in particular from my second link above.

Starfield14 wrote:

Ok, I'll try these recommendations. I' not a programmer and this sounds intimidating but I'll try doing it.

It's a simple application and does not require any advanced skills. Just click the link Eric gave you to read what it is, click the "Download" button, find it in your Download folder and double-click to unzip it. Now move it to your /Applications folder (or anywhere else) and double-click to launch. Copy and paste the results back here. Easy-Squeezy.

You'll see any problems highlighted in red. If you see any that say Adware Remove then click on that and follow the instructions.

Excellent! 🙂