Microsoft Knowledge Base Article 303215 contains the following summary:

The Hfnetchk tool is a command-line tool that administrators can use to centrally assess a computer or group of computers for the absence of security updates. As of the version 1.1 release of the Microsoft Baseline Security Analyzer (MBSA), Hfnetchk is exposed through the MBSA command-line interface, mbsacli.exe /hf. The latest version of the Hfnetchk engine is available in MBSA version 1.2. For additional information about how to obtain MBSA, click the following article number to view the article in the Microsoft Knowledge Base:
320454 Microsoft Baseline Security Analyzer (MBSA) version 1.2 is available


You can use the Hfnetchk tool to assess the security update status of computers that are running Windows Server 2003, Windows XP, Windows 2000, and Windows NT 4.0. You can also use the tool to assess security updates for Internet Information Services (IIS), SQL Server (including Microsoft Data Engine \[MSDE\]), Exchange Server, Windows Media Player, Internet Explorer 5.01, Microsoft Data Access Components (MDAC), Microsoft virtual machine (VM), Microsoft XML (MSXML), Content Management Server, Commerce Server, BizTalk, and Host Integration Server.