So I can't find any evidence of a threat, but I have multiple computers on my network that have all been hit with the same problem. First a little backstory: I have a desktop system (dual boot) that about 90% of the time I use Ubuntu Linux. I rarely use Windows 7 on this computer. I also have a Windows 8.1 tablet computer and my wife has a Windows 8.1 laptop. I first noticed that the network performance (Ookla) on my tablet was dropping to 3Mbps download when it should be closer to 20Mbps, and my Linux desktop was getting normal download speeds. I also noticed that all of my tablet's restore points disappeared, a clear sign that there was some kind of virus, and although I didn't install any suspicious software, I was probably behind my on Adobe Flash updates, and I realized there was an exploit caught in July which could have been the entry point of the malware, either on my wife's computer and/or my tablet. Anyway, I did a complete system refresh (factory new) on my Windows tablet, and it's performance is back to normal. I later discovered that the sluggish performance and stolen network bandwidth was also occuring on my desktop (when booted into Windows only) and also my wife was complaining about problems with her laptop, and I know that she didn't keep things like Flash player up-to-date and was basically relying on the built-in protections provided by Windows Defender.
So, focusing on my desktop, I've tried the following (updated and run AVG scan - no threats found)
Installed and run Malwarebytes (no threats found, inlcuding anti-rootkit scan)
Ran Eset online virus scan (some systweak variants found - scan results attached)
But the problem remains. My computer is slugish and something is stealing roughly 80% of my network bandwidth.
Please help. Thx