Antivirus software?

Question

This might be kind of a silly question and I'm not sure if this is the right place for it. However, in the past I have read two conflicting things on Apple's website regarding antivirus software. One thing I read said it was recommended to have some sort of virus protection. Another thing I read said it was unnecessary.
I used to have the Mac version of Norton Antivirus on my Macbook Pro, however I removed it last year. Is it really necessary to have any kind of virus protection? Because when it comes down to it, anything connected to the Internet can receive a virus. If I don't have virus protection, how will I know if I have a virus? (I ask this because when I used to have PCs I never knew they had a virus until I completed a Norton scan.)
Thanks for your help!

Answer 1

The simple answer is that right now there are no real viruses that affect Macs. There's a few things that can produce some virus-like behavior but there's maybe a handful of these and as long as you don't install any unfamiliar software you are pretty much safe. The other handful can be dealt with almost on a case-by-case basis if your computer shows strange behavior.
Some exceptions are if you have an Intel Mac and run Windows on it, in which case you are really running Windows and are susceptible to anything a PC is. There can also be macro viruses in Office files. I have macros turned off in Office and don't run them unless I know the author.
If you swap files with PC users you can, potentially, pass on a PC virus to them although it won't affect your Mac. If you are in that situation you might think about installing free ClamXAV.
*Mac OSX and Viruses*
There are currently no real viruses that affect OS X users. There are very small number of things that can cause virus-like behavior that can affect Macs under special circumstances. These are:
1) [AppleScript, ASthtv05|http://www.theregister.co.uk/2008/06/23/mac_trojan>
2) DNSChanger Trojan [http://www.f-secure.com/v-descs/trojanosxdnschanger.shtml]
From MacWorld, January 10, 2008:
SecureMac has introduced a free Trojan Detection Tool for Mac OS X. It's available here:
[http://www.securemac.com>
The DNSChanger Removal Tool detects and removes spyware targeting Mac OS X. Called DNSChanger Trojan and also known as OSX.RSPlug. A Trojan Horse the software attacks users attempting to play a fake video file.
Upon attempting to play the video, the victim receives the following message:
“Quicktime Player is unable to play movie file.
>Please click here to download new version of codec.”
Upon running the installer, the user's DNS records are modified, >redirecting incoming internet traffic through the attacker's servers, >where it can be hijacked and injected with malicious websites and >pornographic advertisements. The trojan also installs a watchdog process >that ensures the victim's DNS records stay modified on a minute-by-minute >basis.
SecureMac's DNSChanger Removal Tool allows users to check to see if the trojan has been installed on their computer; if it has, the software helps to identify and remove the offending file. After a system reboot, the users' DNS records will be repaired.
There may be other ways of guarding against Trojans, viruses and general malware affecting the Mac. A white paper has recently been published on the subject by SubRosaSoft, available here|http://www.macforensicslab.com/ProductsAndServices/index.php?mainpage=document_general_info&cPath=11&productsid=174]
3) MacSweeper:
From [Wikipedia|http://en.wikipedia.org/wiki/MacSweeper]:
MacSweeper is malware that misleads users by exaggerating reports about spyware, adware or viruses on their computer. It is the first known "rogue" application for the Mac OS X operating system. The software was discovered by F-Secure, a Finland based computer security software company on January 17, 2008
4) MS Office Macro viruses:
An exception to the "no viruses" is the possibility a macro virus could be present in an Office document and you could help breed that virus if you execute an Office macro. I have my default on Office to run no macros, and always check what the macro will do before I run one (never had to in 10 years of using Office).
5) It is possible to transfer a Windows virus to a Windows machine via a Mac if you copy the infected file and pass it on. [ClamXav|http://www.clamxav.com> is a free, open source virus scanner for Mac OS X that is designed to scan files that you will be sharing with Windows users to assist in making sure you don't pass on viruses to them.
6) Some people have had virus-like behavior appear on web pages due to a service (DNS) supplied by their ISP having a security vulnerability. This isn't your computer but your ISP. Nonetheless, it is a security risk. If you experience strange page behavior (e.g., ads for things on sites where you wouldn't expect those kind of ads) try putting these numbers in Network>TCP/IP>DNS Servers:
208.67.222.222
208.67.220.220
Click Apply. This is an alternate site for DNS which is patched against the vulnerability.
7) If you are using an Intel Mac and run Windows on that computer (or run Windows on a PPC Mac with VirtualPC) you are subject to all the viruses that affect the PC world and should take all the precautions that a PC user would.
[Dave Sawyer post about viruses on Macs|http://discussions.apple.com/message.jspa?messageID=8884756#8884756]
[The Mac Malware Myth|http://www.roughlydrafted.com/2009/01/29/the-mac-malware-myth>
[Should Mac Users Run Antivirus Software?|http://db.tidbits.com/article/9511]
[Trojans in illegal versions of Mac software downloaded from torrents|http://discussions.apple.com/message.jspa?messageID=8892099#8892099]
The tool below is supposed to remove these but commentors observe that only those downloading illegal software are vulnerable to these trojans.
[iWorksServices.clix|http://rixstep.com/2/20090123,00.shtml] 2009-01-23
The following 1198 byte download will rid your system of the iWorksServices trojan without your having to fumble with Terminal and the command line.
[Related information|http://www.technewsworld.com/story/Warning-to-iWork-Pirates-Here-Th ere-Be-Trojans-65944.html]
[Poker Game|http://www.macnewsworld.com/rsstory/63574.html]
The Trojan is masquerading as a program for Mac OS X called "PokerGame." A shell script encapsulated in an application, it is distributed in a 65 KB Zip archive; unzipped, it is 180 KB, according to Intego, one of the security firms that flagged it.