All you have to do is go into Safe Mode. http://support.apple.com/kb/HT1455
Then go into the Applications Folder > Choose MacDefender.app > Move to Trash. (in Safe Mode)
Reboot normally and reset Safari.
Seems to be find after this process.
If you have only downloaded but not installed the file, simply trash the download.
If you have installed the file, then open Activity Monitor and quit the application process. Following that, remove the download file from your downloads folder. After you've done this, open Safari and select Reset Safari. Finally, go to Finder and select your home folder. From here you should select Library, Caches. Select all Cache files (command then A), and move all files to the trash. Empty the trash and restart your Mac.
The application should not affect you from then on.
Here's an extra tip for those who can be a bit of a trigger finger (kids usually click on pop-ups unless you're watching them):
Open Safari and go to it's Preferences. Click on the General tab and un-tick the box "Open safe-files after downloading". This makes it less of an easy task to install downloaded files automatically.
Hopefully this is useful information for you.
It's funny you should mention sophos, i had thought about the whole virus protection thing on my iMac since i first got it last year. But i just felt so safe being on a mac and have only ever had the firewall on as a protection, it's what the mac told me to do, and that's all i did.
But i finally downloaded sophos the other day, i thought it's better to just have it as it seems to have a good reputation.
So I downloaded it and did a full scan of the computer, and....... nothing found, it was fine all along with just a firewall.
I'm so happy not to have to deal with all that virus stuff, and having sophos quietly there in the background is just an extra precaution, I don't even notice it.
Why did you install it in the first place? You have a Mac.
All Mac anti-virus software is pretty much a scam. They can tell you it's to defend the Windows computers so you don't pass on their malware to their systems, but why would you need the Mac to do that? If you are concerned about viruses on a PC, put AV software on the PC, not on the Mac. Run a firewall or appliance that filters all internet traffic to your home network/lan.
Protect the vulnerable Windows computers by running some AV software, have a device between your local/home network to work as a firewall/AV device, and you're good to go. If you click ok, allow and install then dish out your credit card information, well then you need to uncheck the stupid setting in your control panel to fix that.
It's called social engineering, and YOU can fall victim to it just as easily as anyone. A/V is real on the Mac, but like on Windows it won't help against social engineering attacks. These attacks are zero hour attacks and since A/V is a blacklist, it won't know enough about your attack to help you.
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Philip, you need to wake up and smell the coffee. Macs were never invulnerable to viruses (trojans) or malware. That is a common misconception about Macs. The reason why there haven't been many viruses or malware on Macs is because Apple's market share was so small. Windows computers dominated the market and hence why the majority of viruses/malware targeted Windows computers. Since Apple has gained market share and user base, there is more reason for virus/malware creators to create them for the Mac. Viruses and malware are a REAL threat on Macs now. I am a technician and have seen both Mac Defender and Mac Protector and while these are pretty easy to remove, they will only get more complex. Here is a great article stating to "ignore the dinosaurs" who say you don't need virus protection.
And here's an excellent article on how to remove Mac Defender:
I'm one of the dinosaurs. You don't need "anti-virus" software on a Mac, because there are no Mac viruses. If and when a Mac virus appears, I might change my mind.
Mac trojans do exist, and always have existed. The best defense against those is human understanding and intelligence. Where those are lacking, software can't make up the deficiency.
With the sole exception of ClamXav (as far as I know), all "anti-virus" software for the Mac does more harm than good, if it does any good at all.
Sophos "ANTI-VIRUS" for Mac removes Mac Defender and Mac Protector so it does good, contrary to your statement. Your response is stated like a true Mac dinosaur. Even an intelligent person can inadvertently get trojans/malware on their computer. Infections are just going to get even more complex. Mac Defender/Protector is just the start. You do need antivirus, contrary to what the Mac dinosaurs say.
But instead of debating on whether or not Mac viruses exist, let's get back to the OP topic of how to remove the Mac Defender trojan.
Sophos "ANTI-VIRUS" for Mac removes Mac Defender and Mac Protector...
Yes, it does, for the moment. It also causes system slowdowns and kernel panics. Any Mac on which one of those trojans is installed is being horrendously misused, and Sophos doesn't change that.
Infections are just going to get even more complex.
True, and just as on Windows, a more sophisticated trojan will disable or evade "anti-virus" software.
But instead of debating on whether or not Mac viruses exist...
There's no debate. They don't exist.
I have installed it on many Macs and have not had any users report kernel panics or slowdowns because of it.
"Any Mac on which those trojans is installed is being horrendously misused, and Sophos doesn't change that."
Do you personally know the users of these Macs? Again, even intelligent people can get trojans or malware on their computer. Get off of your high horse.
"True, and just as on Windows, a more sophisticated trojan will disable "anti-virus" software."
That is true, but antivirus is still a necessity both in the Mac and PC world. Funny, because other than the OS, a Mac is a PC. I know I am getting off-topic myself, but this begs the question, "Why can't I legally run Mac OS on my PC?" Most current Intel PCs share the same architecture and you can run Windows on a Mac. So why not Mac OS on a PC? Because Apple's hardware sales would tank. Who would buy a $2500 MacBook Pro when they can buy a $1000 PC notebook with the same specifications and load Mac OS on it? Microsoft is taking direct aim at Apple with their current campaign, directly comparing Macs to PCs and how much less a PC with Windows 7 costs.
I am not biased toward either company but I really agree with this. PC notebooks cost a LOT less than Macs and have the same or more functionality. Plus, Windows 7 is an extremely stable and user friendly OS, much like Mac OS is. That brings me to the old Mac vs. PC ads that Apple used to come out with, although funny, were very misleading. The one ad described Apple computers never getting cryptic error messages, hmmm, kernel panics anyone? They are the equivalent to a BSOD. Also, the major complaint I get from people when their Macs break down is that they were under the assumption that Macs never break, they're so much more reliable than a PC. That is a common misconception nowadays as well. Macs used to be rock solid in the pre-Intel days. But nowadays, in my experience, for every 1 PC hardware issue I see, I see at least 5 Mac hardware issues. PCs don't have nearly as many hardware issues as they used to. Apple seems to be putting form over function with their line-up, which result in hardware failures (MacBook Air hinges cracking, Time Capsule hard drives overheating and failing, MacBook top case palm rests cracking, iMacs overheating and failing, etc).