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Security tips for avoiding Trojans and malicious software

<p>Because of the enhanced security features of OS X, such as "sandboxing" techniques for running code, the development of self-propagating "viruses" is difficult and to date we have not seen any for Mac OS X; however, malicious software developers have r

CNET staff
4 min read

Written by Topher Kessler

Because of the enhanced security features of OS X, such as "sandboxing" techniques for running code, the development of self-propagating "viruses" is difficult and to date we have not seen any for Mac OS X; however, malicious software developers have recently released a number of Trojan horse applications for OS X that take advantage of user naivety can be used to steal identities and send spam e-mails through affected computers.

Following the nature of a Trojan horse, most of these malicious software packages are disguised either as legitimate software from Apple or another reputable developer, or more commonly as Internet and QuickTime plug-ins. While antivirus software and Apple's security updates can help combat Trojans and malicious software, it is ultimately up to the user to keep their computer safe from them. Here are some tips for preventing an attack:

  1. Firewall your computer
    Keep your firewall active at all times, except when you need to run applications that are having troubles with the firewall. In these cases, turn off the firewall only when running those applications.

  2. Turn off all sharing services except for those you use
    Many times people will share files and folders, and not even know it. An inadvertent permissions change can result in a shared folder being writable by unknown parties, and while these can be rooted out and made secure again, the best way to avoid getting files dumped on you is to turn off sharing except for when it is needed. This goes for networking technologies as well. Turn off Bluetooth if you do not use it, and do likewise for other "discoverable" features such as the infrared receiver.

  3. Do not download illegal software
    This one should be obvious, but despite the dangers many people are still lured by free illegal software on the internet. The Mac community has seen copies of popular software packages distributed on warez sites after being modified to hide Trojans within them, so even while a package may install the desired program, the Trojan will ride along unnoticed.

  4. Check the checksum!
    Even if you get software from a legitimate Web site, be sure to check the checksum number associated with the downloaded file (if provided), since hackers have been known to infect official downloads with malicious software. We covered how to do this in our article on verifying file checksums. Granted this can be cumbersome, but there are utilities such as Checksum that can make this more convenient do to.

  5. Do not provide your password to a program unless you trust it
    If you are unsure what a plug-in does, perform a Google-search on it to find information on it, and then locate the developer and download from them directly. Many times small companies will release plug-ins for viewing proprietary file formats, so be sure an installer is from a legitimate location before you provide your system password to it. Many plug-ins and software packages do not need to be installed in global system directories to work, and can instead be placed in your user library and applications folders and function just fine for your account.

  6. Only download from the developer
    Many times when surfing the net, a Web site will want you to download and install a plug-in to view the contents of the site, which may be particularly true of porn, hacker, and warez sites. If a Web site provides a quick link to a plug-in download, avoid it and get the download from the developer's Web site directly. For instance, a Trojan can easily be disguised as an update to Adobe Flash, which many people may automatically install because of the name. Be sure plug-ins are from a trusted source. Legitimate plug-ins will always be available from a developer's site.

  7. Do not install unverified software posted on forums (driver hacks, and so on)
    Many times people will post altered system files online for people to install to bring about some hidden functionality of the system software. Since there is no way of verifying what the alterations were, unless the file has been verified by other people do not experiment with it. More than likely a modified system file will be less stable than the original one, and if your system is not functioning correctly, attempt to fix it properly instead of installing someone else's modifications.

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Topher has been an avid Mac user for the past 10-15 years, and has been a contributing author to MacFixIt for just over a year now. One of his diehard passions has been troubleshooting Mac problems and making the best use of Macs and Apple hardware both for family and friends, as well as in the workplace. He and the newly formed MacFixIt team are hoping to bring enhanced and more personable content to our readers, and keep the MacFixIt community going here at CNET. If you have questions or comments for Topher or the other MacFixIt editors, feel free to contact us at http://www.macfixit.com/contact

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