I can't speak for anyone else but I've definitely blocked HTTP downloads successfully and I regularly re-test all the new versions I make to ensure that it does on the games I have that use the HTTP download system exclusively (Evil Genius, Mass Effect 2)  - the tool definitely does block Steam from HTTP-downloading those games here, and definitely redirects my non-HTTP downloads to TelstraClear exclusively because I depend on it myself.

It's worth pointing out that what steam-limiter does for HTTP is to block DNS lookups; if you've already made the Steam client start an HTTP download, it'll have internally cached those DNS results and won't ask for them again, and so they'll get through. Basically, steam-limiter works best when it's run all the time (which should be tolerable given how tiny its memory load is, especially compared to Steam itself), or at least is running before Steam loads (for the HTTP side of things, anyway).

If the limiter doesn't work *at all* for you, then there'll be a reason why, and I'm happy to work with you to try and diagnose it (but here on these forums probably isn't the place). However, I'd start with making sure you have the latest version (v0.5) installed and then per the "How it works" documentation, using DbgView to see whether you get the "filter loaded", "filter unloaded" messages and the like.

For instance, here's some DbgView output I just captured, running limiter v0.5 blocking a post 27030 download:

Code: [Select]

[9572] wlgwpstmcon01.telstraclear.co.nz=203.167.129.4
[9572] SteamFilter hook attached
[9572] CAPIJobRequestUserStats - Server response failed 2
[9572] Connect redirected
[9572] Connect redirected
[9572] Connect redirected
[9572] Connect redirected
[9572] ExecCommandLine: ""C:\Program Files\Steam\steam.exe" steam://open/downloads "
[9572] ExecSteamURL: "steam://open/downloads"
[9572] CAPIJobRequestUserStats - Server response failed 2

Here's some similar output (edited down a lot, since Steam is quite chatty about all your game licenses and such when starting) from me starting Steam and doing an HTTP download:

Code: [Select]

[12632] appdatacache.cpp (451) : Assertion Failed: gameID == k_uAppIdInvalid || gameID == m_unAppID
[12632] appdatacache.cpp (451) : Assertion Failed: gameID == k_uAppIdInvalid || gameID == m_unAppID
[12632] C:\Program Files\Steam\crashhandler.dll
[12632] C:\Program Files\Steam\steamerrorreporter.exe
[12632] C:\Program Files\Steam\steamerrorreporter.exe
[12632] Starting minidump reporter process
[12632] Failed spawning steam error reporter process.
[12632] appdatacache.cpp (451) : Assertion Failed: gameID == k_uAppIdInvalid || gameID == m_unAppID
[12632] appdatacache.cpp (451) : Assertion Failed: gameID == k_uAppIdInvalid || gameID == m_unAppID
[12632] CHTTPRequestCache took 175 milliseconds to initialize
[12632] wlgwpstmcon01.telstraclear.co.nz=203.167.129.4
[12632] SteamFilter hook attached
[12632] Connect redirected
[...lots of "license added" lines elided here...]
[12632] Error: texture file 'graphics\support_flag_left' does not exist or is invalid
[12632] Error: texture file 'graphics\support_flag_right' does not exist or is invalid
[12632] Error: texture file 'graphics\support_flag_top' does not exist or is invalid
[12632] Error: texture file 'graphics\support_flag_bottom' does not exist or is invalid
[12632] ExecCommandLine: ""C:\Program Files\Steam\Steam.exe" "
[12632] CAPIJobRequestUserStats - Server response failed 2
[12632] System startup time: 11.60 seconds
[12632] Error: texture file 'public\steam_cloudsync' does not exist or is invalid
[12632] CAPIJobRequestUserStats - Server response failed 2
[12632] gethostbyname refused
[12632] gethostbyname refused
[12632] gethostbyname refused
[12632] gethostbyname refused

Basically, the above traces show the hook DLL injecting into Steam and initializing itself, and the "connect redirected" and "gethostbyname refused" messages show it doing its thing to fiddle with Windows Sockets underneath Steam. In the case of the Mass Effect 2 download, because it can't contact any of the HTTP content servers, Steam actually fails the download during the "preparing files for install" phase. If you go through a similar process with DbgView and Steam Limiter (preferably the latest version, v0.5 at the moment) running, start Steam, and don't see text like the above then something's likely up and if you contact me directly via gmail then we can look into this further.

People using Windows 7 or Vista (sorry XP users!) will have a firewall capable of this built into their OS. On Windows 7, you can find this by opening Control Panel, then going to System and Security and clicking Windows Firewall. Once there, click "Advanced Settings", which will open "Windows Firewall with Advanced Security".

Go to "Outbound Rules" and click "New Rule".
Select "Custom" and press next, then next again to skip the Program selection screen (you could set this up to only apply to Steam, but it doesn't really matter) and go to the Protocol and Ports screen.
Change protocol type to "TCP" and under "Remote port" select "Specific Ports" and enter "27030", then click next.
Under "Which remote IP addresses does this rule apply to?", click "These IP addresses"
Click "Add..." then "This IP address range:" and enter "0.0.0.0" in the "From:" box and "203.167.129.3" in the "To:" box, then click "OK"
Click "Add..." again and then "This IP address range:" and enter "203.167.129.5" in the "From:" box and "255.255.255.255" in the "To:" box, then click "OK"
Click next to go to the "Action" page and leave this on "Block", click next again to go to the "Profile" page.
On the "Profile" page, depending on your situation uncheck any boxes where you don't want this rule to apply. If in doubt, leave them all checked.
Click next and enter a name in the "Name" box. I called my rule "TelstraClear Content Server", but this is arbitrary.
Click "Finish"

being a girly swot and going in to the uni library over the hols to get books & journal articles for my sports research turns out to have been rather prescient...
wouldn't like to try and find anything in there at the moment...