Microsoft Corp. has released a tool for Internet Explorer 6 that blocks sites from delivering ads when a person misspells an Internet domain name while entering it into a Web browser.

The URL Tracer with Typo-Patrol also tracks when a Web site instructs a person's browser to visit other third-party domains without his knowledge. The scheme is often used in downloading malware to a person's computer to exploit an un-patched IE vulnerability.

The Tracer download, available this week, includes a tool that scans for sites that take advantage of misspellings in an Internet address, a process known as "typosquatting" or URL hijacking." Such sites sometimes serve adult ads on typos of children's Web sites. The tool enables parents to block typosquatting domains.

The tools are the latest releases in Microsoft Research's Strider project, which develops technology for managing computers against security threats.