Hmm...... i dont trust this brazilian version.....
to scan files you are unsure of, it isn't foolproof but it is as good as anything else.
here is the result from 42 AV scans care of virustotal site scan http://www.virustotal.com/reanalisis.html?1167cf027b5d334004aee866dc90b82cc0c645c38e397cc4dcd5225117af5cb1-1281133846
First received: 2010.08.06 22:26:42 UTC
Date: 2010.08.06 22:26:42 UTC [<1D]
Also if you are desperate to play a newer version you can always just edit (with a txt editor like notepad) the steam.inf file and change the version number to what version you like. See Below for method
If you have a server you like and it is running a previous version you could always just edit the file named steam.inf found in C:\Program Files\L4D2\left4dead2 (depedning on your installation path).
Just change the line " PatchVersion=22.214.171.124 " to say " PatchVersion=126.96.36.199 " or whatever version number the other server you like playing on is hosting at the time, when finished playing on that server and you wish to go back to 2.017 or whatever version you have just change the line " PatchVersion=188.8.131.52 " back to its original version number.
Or make archives of this file with winrar or 7zip etc and have one for each version this way you can just "extract file" over the top of one in folder without having to edit it.
The above applies to almost any version except for 2.020 and earlier as the changes in 2.020 are not backward compatible. So if u have 2.019 and dont patch and then use the edit steam.inf method it wont work and you willg et an error, however other versions for eg if u have 2.020 and use the edit steam.inf to 2.021 it will work.