In trying to keep your systems secure there's one technique that will prevent a lot of problems and is simple and usually cheap. That technique is to not tell people what they don't need to know.Just think about it: You wouldn't tell people what credit cards you have so why would you reveal how many routers are in your network and what kind of firewalls you use. These are simply not things that need public disclosure.And most of us extend that idea to our systems. We use network address translation and mail relays to hide our network structure from the outside world. But what about our Web servers?Go to Netcraft (see links below) and you can find out what types of Web servers are used in a domain or at a specific IP address and even whether they are running subsystems such as Perl and Python! Armed with that knowledge crackers and hackers can select their victims with ease.So, why make such information visible?ServerMask from Port80 Software address this problem. It controls what Server header data is visible in HTTP responses and even randomizes the server header between requests to look like one of a number of common servers.ServerMask allows for customization of session cookies, including the Windows-specific ASP session cookies, and can emulate the Apache Web server's HTTP header order. It can disable Microsoft WebDav to suppress its multiple identifiable headers as well as remove the Windows-specific Public header from HTTP responses. ServerMask can also convert Windows SMTP banners to any message.Described by the company as a "super fast ISAPI filter," ServerMask requires only 232K byte for the filter and MMC snap-in extension.And at $49.95 for a single server, ServerMask is not expensive.Also, check out Port80's IIS Security Checklist - a useful list of security issues to think about.