Hello and welcome, DisgruntledCarthaginian:
Disclaimer: I do not personally use Steam & I am only a home user, not staff or a computer expert.
Without the protection logs showing the process and the IP being blocked, it's hard to say for sure.
Some general information:
IP blocks can indicate a number of things:
- They could indicate that MBAM is doing its job of blocking bad content on websites.
- In some cases the blocks are a false positive.
- However, they can also be a sign of infection, especially if the blocks are outgoing and they occur when no browsers are open.
--> There is more information about the IP blocking module in the in the Help Desk topics HERE and HERE and HERE, and in the FAQ - Section G.
They also contain instructions on how to determine what process might be trying to make the connections.
You may also research the IP in question at www.ip-lookup.net or a similar site.
On the other hand, if you think the IP blocks might be a false positive, then please read this pinned topic before starting a new topic in the Website Blocking False Positives sub-forum.
Alternatively, if you think you might be infected, based on the IP blocks and/or other suspicious computer behavior, then please read the following for the available options to have a malware expert assist you with the cleaning process Available Assistance For Possibly Infected Computers.
Under the circumstances, this would probably be the safest plan of action at this time.
The expert help in the malware removal section of the forum is free.
>>Also, you said that you ran both Avast! and Norton 360?
Having more than 1 anti-virus (AV) installed on your system actually increases your vulnerability; it can also cause system slowdowns, crashes and other problems.
When you get assistance for the IP blocks, the expert helping you will undoubtedly suggest that you completely uninstall one or the other.