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As long as I have had Macs, about 12 years, I have NEVER (that I can remember) have a screen freeze on me. My new Macbook Pro just froze while I was on a site www.k6sgh.com/software.html. I got there by looking up Google Earth for my husband who is skittish about downloading to his PC because of viruses and spyware even though he has an antivirus/spyware program on his computer.

I looked up Google Earth/virus to check for him. Landed on this page and it froze. I couldn't even force quit. It was scary.

Can something cause a Mac to freeze other than a virus? I don't just mean Safari is not responding and then I am able to force quit. I manually turned it off then restarted. When I did, the blank light gray screen came on first, then it showed darker gray lines near the bottom, running horizontal across the screen near the bottom third of the screen. I though "Uh oh". Then it loaded up and went back to normal.

I am wondering if I need to spring for an antivirus program which I have never had to do before. I put a free one on my iBook but it could only find viruses (it never did) but not fix the situation should it find anything.

Jitters.... Rita

Hard to say what caused that freeze; visiting the site by itself shouldn't have caused it (my visit was uneventful). Perhaps you can learn more by checking your Console crash logs. I've had similar experiences, albeit rare, and the only way out was to perform a forced shutdown (by holding down the power button until shutdown). It's usually a good idea to give your Mac some time to resolve the issue by itself (forced shutdowns lose data), but that may not work.

Using anti-virus software is not a bad idea, but it shouldn't have to cost you much: utilities like ClamXav are free (donationware), and have nice functions like ClamXav Sentry to keep an eye on your downloads etc.

Wow, I can't believe you went to the site. Brave Soul. What if it did have a virus? Oh, you probably use ClamXav! That's what I used on my iBook but it never found anything, and I got the impression it couldn't fix anything. This version at least has quarantine available. I am downloading it now. Thanks for the link.

P.S. I can't decipher Console Crash Logs.

Rita

Hi: I know this isn't your problem but I downloaded ClamXav. I ran it and got this message: One or more infected files were found, but were left where they are. You can either deal with them yourself, or scan again with the preferences set to move them into a different folder.
I went to the prefs under quarantine but couldn't figure out how to do that. Duh!

Also, I tried to join the ClamXav forum and to prove I am not a robot I have to answer this question: What is the codename for the current version of Mac OS X (ie 10.7)? *

I wasn't sure what they were asking so I put 10.8. That didn't work. I put Mountain Lion and that didn't work. What would you have put in?

Sorry for this.

Rita

10.7 was called "Lion".

I thought I tried that, also. Anyway I tried it and it then said I already had an account! I must have joined years ago and forgot. Sorry about that.

Rita

It's important to realize that most viruses antivirus utilities detect are Windows based, often associated with email. They will not affect your Mac, but should be removed so you cannot unwittingly pass them on to your Windows-using friends.

If you prefer to quarantine* problem files rather than have ClamXav delete them when it finds any, open the Quarantine tab of ClamXav's prefs and click the check box 'Quarantine infected files to'. Then click the button next to it labeled 'Set Quarantine folder...'. You'll be presented with a regular file dialog box, which you'll use to navigate to the folder of your choice, or create a new on on that location. Next click OK on the Quarantine prefs tab, and run the scan again**. Any suspect files will be moved to the quarantine folder; you can use the button 'Open Quarantine folder' on ClamXav's Quarantine prefs tab to quickly access that. (Handy if you forget where you put it...)

Once you're in ClamXav's prefs you should also set the folders to watch (Sentry tab). The folder selection process works the same as before: under the box listing the folders to be watched there are two smaller boxes labeled with + and -. Click on the + to add a folder. That brings up the file dialog again where you can pick one. I recommend you at least add your email program's data folder (Mail's is in your Home folder's Library under Mail) and your Downloads folder (and make sure all your downloads go there). Then check the boxes at the bottom of the tab that say 'Launch Sentry at login' and 'Quarantine Infected files'. Done here.
Next, go to the Prefs' General tab and make sure the top 5 check boxes are checked, including the two update-on-launch boxes. Note that when you use Sentry on login, the virus definitions aren't automatically updated. You need to run ClamXav itself to do that.


*) It's probably best to have ClamXav delete questionable files when it finds them instead of quarantining them, but I'd like to know and record what it finds. When I'm sure I'm not losing potentially important data that might yet be salvaged, I delete the Quarantine folder's content.

**) Full scans of your HD (or users folder) usually don't take all that long, but some items can take an inordinate amount of time. In my case I have a humongous catalog that takes hours to process. Chances that it gets infected are near zero, so I use ClamXav's 'Exclude Files' pref tab to exclude it from regular scans.

Thanks for that detailed explanation. I looked all over the net and couldn't find a decent explanation. Mine doesn't take much time at all. Not much on the drive yet. Besides, I wouldn't know what files to choose. I could leave out the infected ones unwittingly.

What prevents Time Machine or SuperDuper from copying the Quarantine file? Would that cause a problem since they are full of viruses?

OK, now I'm worn out. Thanks for your help.

Rita

I'll deal with your comments in no particular order:

Email scanning:
First off, I suggested above that you checked the email scanning box on the General tab of ClamXav's prefs, PLUS add your email client's mail repository to the Sentry watch list. This may be duplicative, but that's what I do.

I don't know what the problems were with scanning email you came across, but you should know that this flags phishing emails that are otherwise not infected. If you don't open them and click on any links they contain, you won't get into trouble. I wouldn't be surprised if this constitutes the bulk of flagged files. That said, the techniques used to detect some malware ('heuristics' etc.) may produce false positives. If you get a lot of flagged email, or if scanning it starts slowing down your Mac, you might want to look into that, as long as you realize that the flagging ClamXav does may be genuine. It's the same with spam: you might want to check all that in case regular mail is flagged as such, but it could easily become more of a hassle than a help.

Quarantine:
It's always best to (secure) delete malware-flagged files right away, since ClamXav's log should tell you what it detected and deleted (something that you might want to know). Still, quarantining isn't automatically 'fatal', but it could be an issue if you forget about it, like with Time Machine and backup clones you mention.
Note, however, that TM lets you exclude folders. Cloning utility SuperDuper! lets you exclude folders too, but only in the paid version. Carbon Copy Cloner also supports exclusions. I don't know off the top of my head if other cloning utilities allow them.
As to the grayed out Prefs options, that may have been a priority issue, and/or interference from options on different Prefs tabs. For instance, you may have to check Quarantine before you can choose a location for it, or something along those lines.

Sentry vs. Schedule:
Scanning slows down your Mac to various degrees. It's not necessary to watch your entire HD if you use certain folders to corral what comes in from outside, like the folders I mentioned.
To be sure the remainder of your HD(s) is protected too, you may occasionally want to scan everything. That's were Schedule comes in handy, although you could do this manually as well (make sure to adjust your Exclusion list if needed). After all, it isn't like Mac malware is coming at you as from a high pressure hose.

Updates:
There are two types of updates:
- ClamXav itself; this happens not too often
- the virus definition file (the 'APB' of malware); this may be updated daily, or even more frequently if needed.
I mentioned that you may have to run ClamXav to update the definition file, based on my observation that it always does so when I load it, despite the fact that Sentry is always running. I may be wrong here, but it doesn't hurt to make sure the way I do.

Exclusions
When ClamXav is scanning, it lists the full path of the items it processes. If you see it 'stuck' on a particular folder during an exceptionally long scan, this can clue you in to a potential exclusion item.

Thanks, once again, Alternaut. Another good explanation. I'm always biting off more than I can chew. Sometimes I wish I wasn't so curious about computer stuff and just happily reading emails and surfing the net like my hubby and friends. Oh well, that's me.

Thanks again for your input. Helpful as always.

Rita

You're welcome!