Since installing OSX 10 my iMac randomly shuts down and restarts. I can not determine why this is happening. Any ideas?

Launch the Console application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Console in the icon grid.

In the Console window, look under the heading DIAGNOSTIC AND USAGE INFORMATION on the left for crash or panic reports. If you don't see that heading, select

View ▹ Show Log List

from the menu bar.

A crash report has a name that begins with the name of the crashed process and ends in ".crash". It may be under either of the two subcategories, "System" and "User." A panic report has a name that begins with "Kernel" and ends in ".panic".

Select the most recent of each and post the entire contents — the text, please, not a screenshot. In the interest of privacy, I suggest that, before posting, you edit out the “Anonymous UUID,” a long string of letters, numbers, and dashes in the header of the report, if it’s present (it may not be.)

Please don’t post any other kind of diagnostic report, such as a hang log — they're very long and not helpful.

That's not a panic report. Please review the instructions and try again.

Remove the Sophos product by following the instructions on this page. If you have a different version, the procedure may be different.

Back up all data before making any changes.

The version of Sophos you have is outdated, and your profile indicates you have Mavericks. You have to keep software like this up-to-date, especially when you upgrade your system!

As to anti-virus software and the need for it, see my Mac Malware Guide. You can probably do without any anti-virus software just fine.

Why would Sophos be causing a problem?

Because it is no different than any other useless garbage that claims to convey benefits while providing only inconvenience and wasted time.

Is my computer at risk without anti virus software?

It would be, if Apple did not already include everything it requires to protect itself from viruses and malware.

Risk cannot be avoided but threats can be mitigated to an acceptable level. Entrusting your Mac to some magic shield that will protect it and you from all threats is one significant risk you brought upon yourself. The product that can do that does not exist, and many that claim the ability to do so will only cause problems greater than the risk you seek to avoid.

The vast majority of Mac problems reported on this site, including yours, are the direct result of using such junk. If you choose to do so, you own the consequences. It's your Mac, do what you want with it, but the responsibility for properly using and maintaining the software you choose to install is yours.

What antivirus should I use it replace Sophos?

Use what is already included in OS X. You already paid for it. Make it work for you. Read:

OS X Mavericks: Protect your Mac

OS X Mavericks: Protect your Mac from malware

OS X Mavericks: Keep your information safe

OS X About Gatekeeper

About file quarantine in OS X

Seems like I'm exposing the computer to attack!

Your computer is constantly exposed to attack, as long as it connects to the world beyond its enclosure. So are all of mine, and so are millions of others. The most effective defense against attack is your own common sense. Read below.

• Never install any product that claims to "speed up", "clean up", "optimize", or "accelerate" your Mac. Without exception, they will do the opposite.
• Never install pirated or "cracked" software, software obtained from dubious websites, or other questionable sources. Illegally obtained software is almost certain to contain malware.
• Don’t supply your password in response to a popup window requesting it, unless you know what it is and the reason your credentials are required.
• Don’t open email attachments from email addresses that you do not recognize, or click links contained in an email:
  • Most of these are scams that direct you to fraudulent sites that attempt to convince you to disclose personal information.
  • Such "phishing" attempts are the 21st century equivalent of a social exploit that has existed since the dawn of civilization. Don’t fall for it.
  • Apple will never ask you to reveal personal information in an email. If you receive an unexpected email from Apple saying your account will be closed unless you take immediate action, just ignore it. If your iTunes or App Store account becomes disabled for valid reasons, you will know when you try to buy something or log in to this support site, and are unable to.
• Don’t install browser extensions unless you understand their purpose. Go to the Safari menu > Preferences > Extensions. If you see any extensions that you do not recognize or understand, simply click the Uninstall button and they will be gone.
• Don’t install Java unless you are certain that you need it:
  • Java, a non-Apple product, is a potential vector for malware. If you are required to use Java, be mindful of that possibility.
  • Disable Java in Safari > Preferences > Security.
  • Despite its name JavaScript is unrelated to Java. No malware can infect your Mac through JavaScript. It’s OK to leave it enabled.
• Block browser popups: Safari menu > Preferences > Security > and check "Block popup windows":
  • Popup windows are useful and required for some websites, but popups have devolved to become a common means to deliver targeted advertising that you probably do not want.
  • Popups themselves cannot infect your Mac, but many contain resource-hungry code that will slow down Internet browsing.
  • If you ever see a popup indicating it detected registry errors, that your Mac is infected with some ick, or that you won some prize, it is 100% fraudulent. Ignore it.
• Ignore hyperventilating popular media outlets that thrive by promoting fear and discord with entertainment products arrogantly presented as "news". Learn what real threats actually exist and how to arm yourself against them:
  • The most serious threat to your data security is phishing. To date, most of these attempts have been pathetic and are easily recognized, but that is likely to change in the future as criminals become more clever.
  • OS X viruses do not exist, but intentionally malicious or poorly written code, created by either nefarious or inept individuals, is nothing new.
  • Never install something without first knowing what it is, what it does, how it works, and how to get rid of it when you don’t want it any more.
  • If you elect to use "anti-virus" software, familiarize yourself with its limitations and potential to cause adverse effects, and apply the principle immediately preceding this one.
  • Most such utilities will only slow down and destabilize your Mac while they look for viruses that do not exist, conveying no benefit whatsoever - other than to make you "feel good" about security, when you should actually be exercising sound judgment, derived from accurate knowledge, based on verifiable facts.
• Do install updates from Apple as they become available. No one knows more about Macs and how to protect them than the company that builds them.

Summary: Use common sense and caution when you use your Mac, just like you would in any social context. There is no product, utility, or magic talisman that can protect you from all the evils of mankind.

If you find this comment too long or too technical, read only sections 5, 6, and 10.

2. All versions of OS X since 10.6.7 have been able to detect known Mac malware in downloaded files, and to block insecure web plugins. This feature is transparent to the user, but internally Apple calls it "XProtect." The malware recognition database is automatically checked for updates once a day; however, you shouldn't rely on it, because the attackers are always at least a day ahead of the defenders.

The following caveats apply to XProtect:

Gatekeeper doesn't depend on a database of known malware. It has, however, the same limitations as XProtect, and in addition the following:

For the reasons given above, App Store products, and other applications recognized by Gatekeeper as signed, are safer than others, but they can't be considered absolutely safe. "Sandboxed" applications may prompt for access to private data, such as your contacts, or for access to the network. Think before granting that access. Sandboxing security is based on user input. Never click through any request for authorization without thinking.

4. Starting with OS X 10.8.3, a third layer of protection has been added: a "Malware Removal Tool" (MRT). MRT runs automatically in the background when you update the OS. It checks for, and removes, malware that may have evaded the other protections via a Java exploit (see below.) MRT also runs when you install or update the Apple-supplied Java runtime (but not the Oracle runtime.) Like XProtect, MRT is effective against known threats, but not against unknown ones. It notifies you if it finds malware, but otherwise there's no user interface to MRT.

Fortunately, client-side Java on the Web is obsolete and mostly extinct. Only a few outmoded sites still use it. Try to hasten the process of extinction by avoiding those sites, if you have a choice. Forget about playing games or other non-essential uses of Java.

7. Never install any commercial "anti-virus" or "Internet security" products for the Mac, as they all do more harm than good, if they do any good at all. Any database of known threats is always going to be out of date. Most of the danger is from unknown threats. If you need to be able to detect Windows malware in your files, use one of the free anti-virus products in the Mac App Store — nothing else.

♥♥♥♥♥♥♥♥♥♥♥♥♥♥!!!!!!!H0TBABEZ4U!!!!!!!.AVI♥♥♥♥♥♥♥♥♥♥♥♥♥♥.exe

The ClamXav developer won't try to "upsell" you to a paid version of the product. Other developers may do that. Don't be upsold. For one thing, you should not pay to protect Windows users from the consequences of their choice of computing platform. For another, a paid upgrade from a free app will probably have the disadvantages mentioned in section 7.