[kokos76]

Вообще-то у Comodo такая фишка уже реализована »

К сожалению, Вы ошибаетесь. Мне нужно запрет на чтение, а Вы, наверное, имеете в виду запрет на модификацию.
Из хелпа к Comodo:

Protected Files and Folders setting allows you to protect specific files and folders against unauthorized modification especially by malicious programs such as virus, Trojans and spyware. It is also useful for safeguarding very valuable files (spreadsheets, databases, documents) by denying anyone and any program the ability to modify the file - avoiding the possibility of accidental or deliberate sabotage. If a file is 'Protected' it can still be accessed and read by users, but not altered. A good example of a file that ought to be protected is the your 'hosts' file. (c:\windows\system32\drivers\etc\hosts). Placing this in the 'Protected Files and Folders' area would allow web browsers to access and read from the file as per normal. However, should any process attempt to modify it then Comodo Internet Security blocks this attempt and produce a 'Protected File Access' pop-up alert.