A third provision, according to Shapiro, would ensure that Microsoft couldn't restrict through licensing agreements the distribution of third-party middleware to PC makers. In his testimony, Shapiro noted that "competitive threats to leading products often arise from products in adjacent markets. The threats to Windows posed by Netscape Navigator and Sun's Java were of this nature: products that were not operating systems and yet could, over time, undermine the dominant position enjoyed by Windows." He further described the threat posed to Windows by Netscape's browser and Java as "a rare and serious threat." Shapiro went on to review the well-documented means Microsoft used to thwart the competitive threat posed by the two technologies. The economist charged that "Microsoft's illegal conduct significantly raised the entry barriers protecting its Windows desktop monopoly."