Processor: Pentium II 300 MHz.
RAM: 512 MB. 786 recommended
Hard disk: 60 MB free space.
Operating system: Windows 2000 Server SP 1, or Windows 2000 Advanced Server with Service Pack 4, Windows 2003, Windows 2003 Enterprise Edition SP1 or Windows 2003 Server R2.
Other: You must have Adminisator rights to install the antivirus protection. Microsoft ISA Server 2000. The ISASecure antivirus protection must be installed on the same machine as Microsoft ISA Server 2000.

Processor: Pentium III 550 MHz. ISA Server 2004 Standard Edition allows up to 4 CPUs on a server)
RAM: 768 MB. 1GB recommended.Hard disk: 210 MB free space
Operating system: Windows 2000 Server SP 4, Windows 2000 Advanced Server SP4, Windows 2003 Standard, Windows 2003 Enterprise Edition SP1, or Windows 2003 Server R2
Applications: Microsoft ISA Server 2004. Standard Edition SP2 or Microsoft ISA Server 2004 Enterprise Edition SP2

Processor: Pentium III – 733 MHz.
RAM: 768 MB. 1 GB recommended
Hard disk space: 150 MB; additional space required for the content of the Web cache + 60 MB
Operating systems: Windows Server 2003 SP1, Windows 2003 Server R2
Applications: Microsoft ISA Server 2006 (Standard, Enterprise or in array)