Previous 1 2 Next 16 Replies Latest reply: Sep 3, 2014 8:03 PM by MadMacs0
Mark Piaskiewicz1 Level 3 (570 points)

Any opinions? I've been using ClamXav for a long  time and it never seemed to do anything. Avast has flagged emails and found a virus in my Parallels Win 7 file that my Windows AV software eventually cleaned. Avast seems good, any downsides?



MacBook Pro with Retina display, OS X Mountain Lion (10.8.4), 15" 2.7GHz, 16GB, 512GB
  • William Lloyd Level 7 (21,030 points)


  • Barney-15E Level 8 (45,240 points)

    If you really think you need something that causes more problems than it can possibly solve, take a look at Thomas Reed's Anti-Virus testing:

  • Linc Davis Level 10 (184,375 points)

    "Avast" is perhaps the worst of the whole wretched lot of commercial "security" products for the Mac. It's worse than the imaginary "viruses" you were worried about when you installed it. Not only does it fail to protect you, it throws false warnings, destabilizes and slows down your computer, and sometimes or always corrupts the network settings and the permissions of files in your home folder. Removing it may not repair all the damage, and neither will Disk Utility or even reinstalling OS X.

    Back up all data, then remove "Avast" according to the developer's instructions. Reboot.

    If you tried to remove Avast by dragging an application to the Trash, you'll have to reinstall it and follow the instructions linked above.

    "ClamXav" is not routinely needed and should not be relied upon to detect OS X malware. It may be useful for detecting Windows malware in a mixed Mac-Windows network environment, or when a misguided network administrator requires you to run an "anti-virus" application.

  • Topher Kessler Level 6 (9,865 points)

    I haven't used Avast, but recently Thomas Reed tested Avast among many others, and it came out as one of the best for detecting known malware samples (though results may likely vary for different situations). On the other hand, ClamXav did not fare as well.


    However, keep in mind that Avast is one of the AV utilities that installs a number of additional tools, including browser extensions and preference panes, along with some kernel extensions, and this more extensive installation footprint may result in some incompatibilities and problems.


    I usually recommend a lighter-weight AV package that is less intrusive, such as Sophos home edition which has a relatively small footprint on the system. While iAntivirus from the Mac App Store is free and the most self-contained solution (ie, it does not install launch daemons, updaters, and other helper tools), it does not have a built-in updating routine (part of the Mac App Store restrictions, which require updates through the store only), so its definitions may be significantly out of date.

  • Mark Piaskiewicz1 Level 3 (570 points)

    I've had Avast installed for about two months with no ill effects, with the possible exception of the file system shield slowing disk to disk file transfers. I'm still testing this and it's looking like may have been a bug in the prior version. My Mac has to coexist with Windows machines (even itself running Parallels) so I prefer it be malware free.

  • Mark Piaskiewicz1 Level 3 (570 points)

    I read that article as well as one on Ars Technica and that's why I chose Avast. I'll have to look into Sophos and see if it would work for me. I need one that will flag dangerous emails. A smaller footprint would be nice. I wound up with iAntivirus on my Mac but I have no idea how it got there. I used it for a little while but the lack of definition updates made me think it was orphanware so I removed it. I used ClamXav for years but it never struck me as a good solution.

  • Topher Kessler Level 6 (9,865 points)

    To do this you will need one that actively scans incoming e-mail (ie, with some sort of Mail plugin), or which you run on a regular basis with a scan directed at your e-mail client's message database (ie, /Users/username/Library/Mail for OS X's built-in Mail client). I'm not sure of the features of each that will do this, but overall you can configure most to accommodate this need in some way, if it is one you truly need for your setup.

  • Linc Davis Level 10 (184,375 points)

    1. This comment applies to malicious software ("malware") that's installed unwittingly by the victim of a network attack. It does not apply to software, such as keystroke loggers, that may be installed deliberately by an intruder who has hands-on access to the victim's computer. That threat is in a different category, and there's no easy way to defend against it. If you have reason to suspect that you're the target of such an attack, you need expert help.
    If you find this comment too long or too technical, read only sections 5, 6, and 10.
    OS X now implements three layers of built-in protection specifically against malware, not counting runtime protections such as execute disable, sandboxing, system library randomization, and address space layout randomization that may also guard against other kinds of exploits.

    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:
    • It can be bypassed by some third-party networking software, such as BitTorrent clients and Java applets.
    • It only applies to software downloaded from the network. Software installed from a CD or other media is not checked.
    3. Starting with OS X 10.7.5, there has been a second layer of built-in malware protection, designated "Gatekeeper" by Apple. By default, applications and Installer packages downloaded from the network will only run if they're digitally signed by a developer with a certificate issued by Apple. Software certified in this way hasn't necessarily been tested by Apple, but you can be reasonably sure that it hasn't been modified by anyone other than the developer. His identity is known to Apple, so he could be held legally responsible if he distributed malware. That may not mean much if the developer lives in a country with a weak legal system (see below.)
    Gatekeeper doesn't depend on a database of known malware. It has, however, the same limitations as XProtect, and in addition the following:
    • It can easily be disabled or overridden by the user.
    • A malware attacker could get control of a code-signing certificate under false pretenses, or could simply ignore the consequences of distributing codesigned malware.
    • An App Store developer could find a way to bypass Apple's oversight, or the oversight could fail due to human error.
    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. OS X 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 presumably effective against known attacks, but maybe not against unknown attacks. It notifies you if it finds malware, but otherwise there's no user interface to MRT.
    5. XProtect, Gatekeeper, and MRT reduce the risk of malware attack, but they're not absolute protection. The first and best line of defense is always your own intelligence. With the possible exception of Java exploits, all known malware circulating on the Internet that affects a fully-updated installation of OS X 10.6 or later takes the form of so-called "trojan horses," which can only have an effect if the victim is duped into running them. The threat therefore amounts to a battle of wits between you and the malware attacker. If you're smarter than he thinks you are, you'll win.
    That means, in practice, that you never use software that comes from an untrustworthy source, or that does something inherently untrustworthy. How do you know what is trustworthy?
    • Any website that prompts you to install a “codec,” “plug-in,” "player," "extractor," or “certificate” that comes from that same site, or an unknown one, is untrustworthy.
    • A web operator who tells you that you have a “virus,” or that anything else is wrong with your computer, or that you have won a prize in a contest you never entered, is trying to commit a crime with you as the victim. (Some reputable websites did legitimately warn visitors who were infected with the "DNSChanger" malware. That exception to this rule no longer applies.)
    • Pirated copies or "cracks" of commercial software, no matter where they come from, are unsafe.
    • Software of any kind downloaded from a BitTorrent or from a Usenet binary newsgroup is unsafe.
    • Software that purports to help you do something that's illegal or that infringes copyright, such as saving streamed audio or video for reuse without permission, is unsafe. All YouTube "downloaders" are in this category, though not all are necessarily harmful.
    • Software with a corporate brand, such as Adobe Flash Player, must be downloaded directly from the developer’s website. If it comes from any other source, it's unsafe.
    • Even signed applications, no matter what the source, should not be trusted if they do something unexpected, such as asking for permission to access your contacts, your location, or the Internet for no obvious reason.
    6. Java on the Web (not to be confused with JavaScript, to which it's not related, despite the similarity of the names) is a weak point in the security of any system. Java is, among other things, a platform for running complex applications in a web page, on the client. That was always a bad idea, and Java's developers have proven themselves incapable of implementing it without also creating a portal for malware to enter. Past Java exploits are the closest thing there has ever been to a Windows-style virus affecting OS X. Merely loading a page with malicious Java content could be harmful.
    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.
    Java is not included in OS X 10.7 and later. Discrete Java installers are distributed by Apple and by Oracle (the developer of Java.) Don't use either one unless you need it. Most people don't. If Java is installed, disable itnot JavaScript — in your browsers.
    Regardless of version, experience has shown that Java on the Web can't be trusted. If you must use a Java applet for a task on a specific site, enable Java only for that site in Safari. Never enable Java for a public website that carries third-party advertising. Use it only on well-known, login-protected, secure websites without ads. In Safari 6 or later, you'll see a lock icon in the address bar with the abbreviation "https" when visiting a secure site.

    Follow the above guidelines, and you’ll be as safe from malware as you can practically be. The rest of this comment concerns what you should not do to protect yourself from malware.

    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 the free software  ClamXav— nothing else.
    Why shouldn't you use commercial "anti-virus" products?
    • Their design is predicated on the nonexistent threat that malware may be injected at any time, anywhere in the file system. Malware is downloaded from the network; it doesn't materialize from nowhere.
    • In order to meet that nonexistent threat, the software modifies or duplicates low-level functions of the operating system, which is a waste of resources and a common cause of instability, bugs, and poor performance.
    • By modifying the operating system, the software itself may create weaknesses that could be exploited by malware attackers.
    8. ClamXav doesn't have these drawbacks. That doesn't mean it's entirely safe. It may report email messages that have "phishing" links in the body, or Windows malware in attachments, as infected files, and offer to delete or move them. Doing so will corrupt the Mail database. The messages should be deleted from within the Mail application.
    ClamXav is not needed, and should not be relied upon, for protection against OS X malware. It's useful only for detecting Windows malware. Windows malware can't harm you directly (unless, of course, you use Windows.) Just don't pass it on to anyone else.
    A Windows malware attachment in email is usually easy to recognize. The file name will often be targeted at people who aren't very bright; for example:
    ClamXav may be able to tell you which particular virus or trojan it is, but do you care? In practice, there's seldom a reason to use ClamXav unless a network administrator requires you to run an anti-virus application.
    9. It seems to be a common belief that the built-in Application Firewall acts as a barrier to infection, or prevents malware from functioning. It does neither. It blocks inbound connections to certain network services you're running, such as file sharing. It's disabled by default and you should leave it that way if you're behind a router on a private home or office network. Activate it only when you're on an untrusted network, for instance a public Wi-Fi hotspot, where you don't want to provide services. Disable any services you don't use in the Sharing preference pane. All are disabled by default.
    10. As a Mac user you don't have to live in fear that your computer is going to be infected every time you install an application, read email, or visit a web page. But neither should you have the false idea that you will always be safe, no matter what you do. The greatest harm done by security software is precisely its selling point: it makes people feel safe. They may then feel safe enough to take risks from which the software doesn't protect them. Nothing can lessen the need for safe computing practices.

  • Mark Piaskiewicz1 Level 3 (570 points)

    Avast does this by default, that's why I zeroed in on it in particular.

  • Mark Piaskiewicz1 Level 3 (570 points)

    Good article. I've been an Apple user for almost 30 years and never had a virus but I (begrudgingly) run Windows on the Mac as well as having a number of friends who also use Windows so an AV program on the Mac is the first line of defense. As long as it works and remains unobtrusive I have no problem running it. As far as safe computing practices, after all these years I better know what I'm doing or I deserve what happens.

  • MadMacs0 Level 5 (4,700 points)

    Mark Piaskiewicz1 wrote:


    My Mac has to coexist with Windows machines (even itself running Parallels) so I prefer it be malware free.

    You should not rely on any Mac A-V software to protect your Parallels processes. Most will do an adequate job of finding Windows malware on the Mac side, but you should run a separate A-V product on the Windows side to cover all your bases there.

  • MadMacs0 Level 5 (4,700 points)

    The ClamAV® scan engine was originally an e-mail scanner and Apple still distributes it with their OS X Server software for that purpose. You do have to be cautious not to allow any A-V software to move or delete e-mail as it will certainly corrupt the mailbox index, which can result in several mail issues down the line.

  • MadMacs0 Level 5 (4,700 points)

    When I read this earlier today, I thought I should respond when I had time, but Topher said almost everything I would have said (no surprise) so I'll limit my remarks on Avast! to one entry in the Comment section of Thomas Reeds test article when responding to a question of why Avast! wasn't a "no-brainer" choice:

    Although avast! certainly has a high detection rate on its side, keep in mind that there are any other factors that should determine which anti-virus software you use. Do not rely solely on testing like this to make the choice. Evaluate the features that you feel you need that each program offers, and make sure that you educate yourself as to what the risks actually are before installing anything.

    As far a ClamXav is concerned, the unfortunate thing about it is that it must rely entirely on a scan engine provided by others. Don't get me wrong, it's a very good scanner and improvements are being frequently rolled out by Sourcefire/ClamAV®, but in the end it is the signature database that matters. Signature writers are working much harder these days to keep up, but they are totally reliant on samples being submitted to their site or to VirusTotal. They don't have a 24-hour watch center looking for new outbreaks or a lab to do detailed analysis of what the malware does and how it does it. It's mostly up to users and the other subscribers to VirusTotal to share what they find. I've been through more than one epidemic here in the forum and the last thing most users want to be bothered with is providing a sample of what infected them. They will stop at nothing to make it disappear forever and have no idea where it came from.


    That being said, there are several of us available to work around the clock here to obtain samples of any new Mac malware and get it to any and all A-V vendors capable of putting a stop to it, but as I said it takes some user cooperation to do that. It doesn't happen very often, but ClamAV did have at least one new variant in it's database before Apple or any other A-V software we tried. But that is very much the exception. Commercial software can easily afford to commit the resources necessary to stay on their game, where a not-for-profit organization has no chance of keeping up.

  • giodis Level 1 (0 points)

    An excellent article !.

Previous 1 2 Next