Antivirus Software is a Hack

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+ I read a really terrific article today about computer security and + really dumb ideas or trends that have developed in this field. It's + M. Ranum's The Six Dumbest Ideas in Computer Security, and I highly recommend reading through the whole thing. It's got + great anecdotes and really simple language for what I consider to be + some of the obvious issues with the way programmers and sysadmins think + about security (myself included). One portion of it (idea #2), however, + finally put something into words that I've felt for a really long time. + It enables me to explain why I think all antivirus software is a total + hack and is virtually useless. +

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+ hack
+ 1. n. Originally, a quick job that produces what is needed, but not + well. +

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+ This is the Jargon File's definition of a hack. And to me, this is what + antivirus software is. Antivirus software, as I understand it, emerged + in the mid to late 1980s and became prolific in the 1990s. In the 2000s + it was considered an essential piece of software and people were paying + for yearly subscriptions for antivirus suites from Norton, Avast, and + McAfee. +

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+ The most basic functionality of an antivirus program is to determine + whether malware exists on a host operating system. The typical method of + doing this is to use a collection of virus definitions and compare each + and every potentially-infected file with each and every definition to + determine whether the file is malware or has been infected by some. An + over-simplified way of implementing this is to store a collection of + hashes, each taken from a known potentially unwanted program or + infectious executable. You can then hash entire files or portions of + files and compare the checksums to see whether a file contains or is + equivalent to the definition, and is therefore infected and shouldn't be + executed. Some security suites go beyond this with heuristic matching, + but if you run an antivirus that has to "update definitions" on a + routine basis, it probably works something like this*. With any luck, it + does it without being a total detriment to system performance. Ideally + it also doesn't act like a piece of malware itself by making itself near + impossible to remove (looking at you, McAfee). +

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+ To me, a virus definition database is "enumerating badness" (Ranum's + Dumb Idea #2). The premise is that it is not only logical but even + possible to compile a list of all potentially unwanted + programs, viruses, ransomware, and worms. An environment of trust should + be built around the programs that you want to run (read: + allow to run), not the other way around. Picture an operating + system where no binary file can be executed unless it is specifically + flagged as being allowed to. Oh and picture also being able to restrict + this execution to just the file's owner, or other groups of users. + Wouldn't it be easier to store the list of 30 odd programs that you and + other system users trust to be run than the thousands (millions?) of + programs that are infectious, forbidden, or unwanted? What about when + those trusted applications become compromised? Would it not also be + easier to maintain a list of checksums for those binaries and compare + those checksums before they're executed to make sure they haven't been + infected or replaced? +

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+ The answer is yes, it would be easier. And yes, it is easier. Of course, + your system has to work that way. Antivirus software is a hack because + it's a hack-y solution to a problem that has a better, simpler solution. + It also has the potential for making a ton of money but I won't go into + that. It's easier to enumerate goodness, to specifically open up to a + select few trustworthy applications. Good lists are usually shorter than + bad lists. This builds on top of Ranum's Dumb Idea #1: Default Permit. + You wouldn't configure a firewall to just block some known bad ports and + traffic. You configure it to block all of it, and then whitelist the + ones you know you can trust. You wouldn't configure a browser ad-blocker + to permit all ads, and select the ones you don't want to see. You block + all of them! Then, if there are sites or ads you're okay with seeing, + you whitelist them. You shouldn't default permit all programs to be + given control over your computer, and then meticulously list the ones + that don't have that permission. +

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+ Oh and of course, as always, there's free software that lets you do + this. You don't have to pay for an antivirus suite, or even use an + unpaid one that slows down your computer or barrages you with ads. On + the BSDs and virtually all Linux distributions, there are built-in tools + to control access and execution of binaries. There are additional tools + that you can install that check whether binaries (in locations like + /bin or /usr/local/bin have been modified + since you last used them. On Windows, the story is a little different. + Most home Windows 10 users are automatically allowed to install and run + any software they want to by default. Windows Server does have Software + Restriction Policies that allow you to create a "default deny" policy + and whitelist only the software that's allowed to run. If you're using a + home edition you probably have to look for software that lets you do + this. I haven't tried any of them so I'm not going to endorse or even + name them here. +

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+ Preventing malware from running on your system is a problem. Solving + this problem is the right thing to do. But please, try to solve it the + right way. I stopped using an antivirus after I moved out and got to + control my own computer. I don't think it ever did me any good besides + flag false positives (a lot of the time with programs or applications + that I wrote, which weren't malicious in any way!) and grind my spinning + disk to a halt. Evaluate what software you use. Is most of it online? + Are there one or two applications that you know you need to use? How + often do you install and use unknown or untrusted software? Odds are you + can come up with a list of very few programs that you want or need to + use. If it's less than 100,000, you're probably better off with a + default deny policy than an antivirus suite. +

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+ * What I didn't mention here is that as soon as a new piece of malware + is constructed, if it's different enough from its predecessors, it's + impervious to all antivirus suites on the planet that don't have it in + their definitions. So until that malware is used, detected, and added to + the list, it has free reign. +