Well, you've got two (Tux the) Penguins and a Wizard (Likes) from Brian and Stan and I, so you can see we've all been rooting for you.
That's great news.
Before I go on and suggest a few housekeeping tasks to assign to your Lubuntu, I'll tell you the most important one.
UFW is the Uncomplicated Fire Wall, it is installed by default, but not enabled currently. Between UFW and a firewall at your modem-router, many many Linux users are effectively safe from "The Nasties" and don't even have to consider Antivirus (AV) software, nor anti-malware software ... PROVIDED they practise safe surfing.
At your Menu button bottom left, under System Tools is LXTerminal, the Terminal for the LXDE DE (Desktop Environment) you are using with Lubuntu.
Click it to launch, and at the prompt type in and enter
If (I hope) you set a password when installing Lubuntu, you will enter that password there, and you will be rewarded with a message that UFW is enabled, in real time, ie for the rest of your session, that a startup script has been generated, and that it will run at each and every startup/boot/reboot.
A good basic article on UFW is here
and it also links to one on GUFW which is the graphical frontend for UFW, and tells how to install that if you prefer Point and Click.
Important to note from that article, is in part, as quoted
Default rules are fine for the average home user
When you turn UFW on, it uses a default set of rules (profile) that should be fine for the average home user. That's at least the goal of the Ubuntu developers. In short, all 'incoming' is being denied, with some exceptions to make things easier for home users.
I'll get cracking on that short list of things to do, probably Post it in a day or three.
Can you do me a favour in the meantime, and post the output of two commands from Terminal?
(my comments are preceded with a # and are not commands)
The latter one (free) should be performed with no Firefox or other apps running, that is basically from the desktop.
Cheers and enjoy your Lubuntu