After running the definitions update, the software gave me an error and asked to close. When I tried to restart Avast, I received yet another error message. The message I've been dealing with was "can not initialize avast! engine: Invalid argument." After a bit of poking around, I got it working by tweaking a kernel variable. I did my troubleshooting by running Avast in the CLI.
As root (not sudo), I entered this into the terminal:
echo 128000000 >/proc/sys/kernel/shmmax
Now the next hurdle was to discover that Avast wants to me seek out a license key. Unlike Bitdefender though, this release of Avast isn't trialware. So asking me to fill out a form and then wait for 20 minutes is just stupid. Finally, the registration code arrived and I was able to get everything registered.
From the Unity dash, I launched Avast. I was again asked for my registration code. I entered it and I was finally ready to use the software. Unlike ClamTK/ClamAV, Avast doesn't offer scheduled scanning. Instead, you can only schedule virus definition updates. On the plus side, I've "heard" that Avast does a little better with malware and rootkits, than other programs. So for that reason, I find myself leaning with Avast more than other programs.
Now that we have had a look at handling malware, it's time to think about more Linux specific security concerns.
On any Linux distribution, including Ubuntu, your firewall needs are going to be handled differently than you might be used to on Windows. To take the sting out of this – and assuming that firewall protection for the Ubuntu workstation takes place exclusively at the local level – I recommend using GUFW.
Using Ubuntu's firewall tool, known as "uncomplicated firewall" or UFW, the GUFW application adds a nice user interface to UFW for newbies. Adding or removing ports for specific applications is brain-dead easy with this software. Even better, you can go to advanced mode and handle specific ports over varied protocols.
File sharing considerations
Another area to be wary of is file sharing. Many of us, might be tempted to simply run with Samba shares and let our data flow freely between PCs. This is a bit messy and potentially puts your system at risk.
Instead, I recommending sharing folders over OpenSSH. And when using SSH, do not rely on SSH passwords for protection. Regardless of which port you setup for SSH, you will be hit all day long by brute force password attacks.
I recommend going with a RSA key instead. It's also worthwhile, in my opinion, to disable "PermitRoot" and run SSH on a non-default port. All of these things together will help to "harden" your SSH security.
Updates and encryption
Two other items on my basic security list are keeping your workstation updated with the latest updates, and if you like, encryption for sensitive data.
The updates, are fairly obvious _ when Ubuntu prompts you to update security updates, do so. As for the encryption, I recommend reading up on encfs for folder encryption and GPG encryption for email. Neither of these two options are a "must do," however they do offer you privacy from prying eyes.
And last but not least, if you're visiting a coffee shop or perhaps browsing on a public wi-fi network, I recommend looking into Tor for browsing privacy. Because software is readily available that lets other users snoop on what you're doing online, even your login details for various sites, privacy matters.
To be clear, this isn't a replacement for https on websites for banking or other sensitive matters. Instead, Tor merely offers you a means of adding a layer of privacy on the data being sent into the Tor network.
If the Tor installation you're using is only for coffeeshop web browsing, I recommend the Tor configured release of Firefox. It's ready to go out of the box and dead simple to use. If you need better protection, then you might look into OpenVPN instead.