June 21, 2006

Bypassing of web filters by using ASCII

Kurt Huwig writes "InternetExplorer does not only ignore NUL bytes, but also the most significant bit of webpages encoded in ASCII. Most virus scanners and web filters do not ignore this bit, which offers a new way for virus writers and spammers to bypass these filters. Opera 8/9 and FireFox 1.5 treat these files as ISO-8859-1 which is wrong, but makes them invulnerable to this threat."

Link: iku-ag.de


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