oh how is that . i use an ipstar satalite reciever no real software ????
If you don't have a router, then you don't have a firewall in it of-course.
Most attacks are not something a firewall would block anyway, it's initiated by the user, which the firewall views as proper action. Meaning most viruses start with someone running a bad file or going to an infected web site. Since you initiated that action, the firewall lets it though.
As far as security? You can run Kaspersky, and use it's firewall also, but it's not fully needed because the routers have a firewall. Do not need to run MS Defender or any other second anti-virus. I run Malwarebytes but not the resident program, just do a scan every so often. But I keep track of what sites I visit and most techs know the signs of a bad site or email that may have viruses. Running the full version of Malwarebytes along with another anti-virus product is OK.