A client was having an intermittant error on websites he is hosting on one of his servers. The error was occurring only on some pages and only some of the time. The error message displayed was “The request was rejected by the HTTP filter. Contact your ISA Server administrator. (12217)”. He asked me to have a look.
I tried a couple of pages on the sites and sure enough the error was occurring intermittantly. I put the error message into Google Groups and the only hit with an answer was in German!
I put the resolution into Altavista’s Babelfish translation service and discovered that I had to:
Click on Firewall Policy
->Right-click on the website publishing rule
->Select Configure HTTP
->On the General tab ->de-select Block high bit characters
Having done this, the sites worked with no errors – ISA Server 2004 blocks characters like √ï¿½, √ï¿½ and √ï¿½ by default and the only way to stop pages with these characters being blocked is to use this fix.