Cellist wrote: ↑Fri May 05, 2023 1:04 pm
... for me it changed within a couple hours after I activated the filter. Since I haven't detected any malware, can't I just assume the IP was blocked because of another shared user?
A rule of network security: Never assume
Anti-virus and anti-malware software is not even
remotely dependable. When I was in IT, I regarded it as the
last line-of-defense, and a poor one at that. Besides: The bad guys are exploiting more than PCs and servers. They are compromising IoT (Internet of Things) devices (appliances, home automation, etc.), as well.
One of the best defenses you can employ is a border router security stance called "That which is not explicitly allowed is denied." Blocking port 25 for both ingress and egress is an example of that. Certain things, certain IoT devices, for example, that don't
need Internet access should be blocked at the Internet border router entirely. E.g.: The network-connected IP cameras for my video surveillance system have no business accessing the Internet. So they're assigned to an IP block, the entirety of which is blocked for egress at the border router.
Nothing on my LAN should be doing file sharing to the Internet, so all the common file sharing ports are blocked for the entire LAN.
Customers don't "share" IP addresses, per se. "Share" as in "more than one using the same IP at the same time." They share an IP address space pool, where there are X number of IP addresses in a block and any particular customer may get any particular IP address out of that block at any particular time.
Some ISPs force frequent IP address changes. Some do not. I've friends that have been on WOW and Comcast/Xfinity that have held the same dynamically-assigned IP address for months on end. Conversely: I know, from personal experience, that AT&T and T-Mobile wireless networks force frequent IP address changes. (Plus T-Mobile, at least, does a thing called CGNAT [Carrier Grade Network Address Translation]), so the IP address you're assigned is not the IP address the rest of the Internet sees.)
