Honestly, I'm quite surprised about the strong reaction. I thought it was common knowledge that this kind of software is full of bugs.

During the last year, I discovered dozens of bugs in different widespread anti-virus products. Not all of them can be as easily explained as this one and only a few a as critical as this one, but still...

Concerning your question: In general, I consider it quite difficult (if not impossible) to give a concrete answer. The software, as it is now, is just in a horrible state. Depending on what your threat model is, how experienced you are as a user, it might very well decrease your system security.

Yes. For organizations the harm is compounded because IT and users don't understand how limited AV is. They think AVs have good detection rate, and they think AVs can generally "disinfect" your computer when you get pwned, and think AV doesn't increase attack surface. This leads to the false conclusion that it's an acceptable risk to use Acrobat Reader and open attachments in Office etc.

My own thought process on this is the following: Some parts of antivirus software do good work. Understanding that antivirus software is no substitute for real security, but more like a helpful layer to try to catch things that otherwise might sneak in, helps a lot in using it successfully. On that level, software which scans downloaded files before opening them, and periodically scans the filesystem passively for any known threats, is not bad. I agree that patching the software of its bugs in the first place is a better goal, but it doesn't hurt to have an in-between option that helps out a little bit. Of course, such software rarely needs to be a third-party suite, as Microsoft's own Windows Defender software performs this task decently.

Where things get hairy are antivirus suites in particular. It's one thing to passively scan files, but AV suites have a bad habit of hooking into the operating system and making other changes, usually in the name of real-time monitoring. This is where I feel their supposed benefits fall flat. It would be one thing if these hooks were also passive, but Windows and most other operating systems make it difficult to access the kernel's data on purpose, and I don't trust an antivirus suite to do so in a safe manner. It's one thing for an exploit to compromise passive scanner running with userland permissions, and another thing entirely to exploit an AV suite with direct kernel access. The latter can cause the security features to backfire pretty hard.

>this is the second AV fiasco in recent months

First of all, this bug was fixed nine months ago (see Timeline).

This is in no way a "fiasco", this is normal process of improving security of the product. Bug reported and timely fixed, bounty paid, no exploit was found in the wild, no harm done. You can count yourself number of similar bugs fixed in Chrome or Firefox this year.

>is it safe to say that running an antivirus is actually increasing your risk instead of decreasing it?

Yes, running ANY software on your computer increases attack surface, thus increasing risks. In the same time running AV decreases many other risks.

My opinion is all in all AV still does more good then harm today, provided it's actively developed by credible shop and timely updated.

Erm, it seems you haven't been paying attention. This is the second AV fiasco in the last two days.

It's been the case for decades now. Guess the world is finally catching on.

Write parsing for complicated formats in C/C++. Run it on suspicious files from the outside world. What could possibly go wrong? Play stupid games, win stupid prizes.

In order to fight the virus you have to become like a virus in many ways. Like them, you have to hide your own code in order to avoid detection. You have to get down to their level and use dirty tricks.

It's more than the 2nd, and yes, it's safe to say that.