Steam, created and maintained by Valve Software, is a digital distribution client that allows users to purchase, download and play PC games from the Internet. Some firewall programs, such as PeerBlock, block access to Steam, preventing your computer from connecting to Steam's servers. This can make it impossible to use Steam or, if you have already purchased games from Steam, impossible to play them. To use Steam and PeerBlock together successfully, you must add Steam to the allow list on your PeerBlock software.
Launch the PeerBlock software from your computer.
Click "List Manager" followed by "Add."
Type "Steam" in the description field.
Click "Add URL." Enter the URL "http://list.iblocklist.com/?list=steam" (without the quotation marks).
Select "Allow" as the type and click "OK" to save all changes. PeerBlock will allow Steam access and you will be able to connect to Steam.