http://uk.trendmicro-europe.com/enterprise/support/knowledge_base_search .php ..enter 18070 for the solution id: Title: [Hot Fix Information] InterScan WebProtect 3.0 for ISA hot fix - Build 1061 HTTP module Problem: Once applied, this hot fix will provide a "KeepHttp11" option key under the [HTTP-Scan] section to toggle on/off any changes from build 1045. With a "KeepHttp11=yes" setting, users are allowed to connect through an ISA proxy with the "Use HTTP 1.1 Through Proxy Connection" option enabled in Internet Explorer browser. However, by doing so, the user machine is subject to a vulnerability regarding chunked encoding data transfer through HTTP 1.1. Refer to the attached hotfix_readme_ISWP3.0_B1061.txt file for more information about this hot fix. Solution: Contact Trend Micro Technical Support to request for the ISWP3.0_Hotfix1061.zip file, which should only be installed on servers running ISWP 3.0. Premium Support Program (PSP) clients can contact their Technical Account Manager (TAM) directly. NOTICE: This hot fix was developed as a workaround or solution to a customer-reported problem. As such, this hot fix has received limited testing and has not been certified as an official product update. All mail from this domain has been virus-scanned.