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One of the family's computers is a Macbook Air, recently the virus subscription expired and my problem is to decide whether to renew/replace it. When the Mac was bought (2010), the anti virus program was part of the package. Friends and colleguages said at that time that "Macs don't get infected with viruses".

The machine is now mainly used by my children for browsing (no social media) and for Skype.

When I researched the topic on this site, it seemed to me that the Q&A were a bit dated, see OP:s regarding Mac and anti virus, so I am unsure about their validity.

So my questions is: Explain to me in a practical, fact based way the risks of not running an anti virus on a Mac that is mainly used by "pre teens" for surfing with Chrome and using Skype?

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@DanielBeck, good points! It will help me to decide, already leaning towards having virus/malware. I will try to edit the question to get it open again –  FredrikD Jul 27 '12 at 17:14
    
As this topic has been reopened, I reposted my comments as answer. –  Daniel Beck Jul 29 '12 at 15:26
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3 Answers

up vote 4 down vote accepted

Any system can be the victim of malware. For example, the technological difference between e.g. your friendly desktop search indexer and a malware syphoning of your private data is negligible.

That said, there has been no (well-known) malware so far for OS X that:

  1. Did not require active user involvement (like starting the program) and
  2. worked without exploiting a vulnerability in essentially 3rd party code (e.g. Flashback used Java, which is no longer installed by default anyway).

Some malware even requires users to enter their Administrator password during the installation.


Anti-virus software uses two basic mechanisms to detect malware:

  • Known malware is identified through a specific pattern provided in the database by the anti-virus vendor. This is only capable of identifying widespread, known malware and requires you to keep your AV product and subscription updated.
  • Dynamic (behavioral) and static (structural) characteristics of programs. This leads to false positives with software with legitimate use cases (like remote desktop/remote control software), and false negatives if there's no behavior legitimate software doesn't use — malware can still transfer your personal data to some remote server, and look as harmless as Dropbox or some other cloud/local syncing service.

So, while malware for OS X exists, it's far from the "receive a packet over the network and you're infected" quality that plagued early Windows XP. It's mostly trojans, exploiting social behavior patterns and other user vulnerabilities, instead of the OS. And for those, it really depends on how tech-savvy your users are.


OS X Mountain Lion, released earlier this week, includes Gatekeeper, a security feature that should keep most of these malware exploiting users' gullibility out, by only allowing execution of downloaded programs that are signed by developers registered with Apple.

If you don't give your users administrative access and the power to run arbitrary software, instead restricting them e.g. to the App Store, you should be as good as technically possible. Remember, an AV product is no panacea.

Note that this is no excuse to skip doing backups, run software downloaded from file sharing networks or file hosters with unknown origin, and other similar sense precautions.

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The risk is that you will get a virus/trojan that will do you/your finances/your reputation some damage. Do you want their communications bugged, or their bank account logins stolen? Would they want their facebook accounts hacked and pornographic pictures put up? These could happen.

There was the Flashback Trojan in 2011, and see this article on ZDNet for the latest Mac Malware:

A new Mac OS X Trojan referred to as OSX/Crisis silently infects OS X 10.6 Snow Leopard and OS X 10.7 Lion. It then spies on the user by monitoring Adium, Firefox, Microsoft Messenger, Safari, and Skype.

The days are long gone that a Mac or Linux user could feel safe while laughing at the trauma Windows users faced.

Now - get antivirus/antimalware to help protect you and others.

If you want further information on information security risks - visit http://security.stackexchange.com

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Good input on OSX/Crisis! I googled it and found good references. I checked out similar questions at the security site, the one that I found most relevant was: security.stackexchange.com/q/5763/11592 The OP asked about why anti virus at all. –  FredrikD Jul 27 '12 at 17:18
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With a bit of common-sense, antiviruses are not needed - especially on Linux/OSX.

  • Never install cracked apps
  • Never give super user permissions on apps that you don't understand why they 'd need to have them.
  • Keep your system updated
  • Disable flash/java and enable them on purpose per site only.

Keep in mind that anti-viruses can only protect from old threats - and making a detected malware "safe" from anti-virus detection is totally trivial (and automated).

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