The Comodo Group, an Internet security company, has been attacked in the last month by a talkative and professed patriotic Iranian hacker who infiltrated several of the company’s partners and used them to threaten the security of myriad big-name Web sites.

But the case is a problem for not only Comodo, which initially believed the attack was the work of the Iranian government. It has also cast a spotlight on the global system that supposedly secures communications and commerce on the Web.

The encryption used by many Web sites to prevent eavesdropping on their interactions with visitors is not very secure. This technology is in use when Web addresses start with “https” (in which “s” stands for secure) and a closed lock icon appears on Web browsers. These sites rely on third-party organizations, like Comodo, to provide “certificates” that guarantee sites’ authenticity to Web browsers.

But many security experts say the problems start with the proliferation of organizations permitted to issue certificates. Browser makers like Microsoft, Mozilla, Google and Apple have authorized a large and growing number of entities around the world — both private companies and government bodies — to create them. Many private “certificate authorities” have, in turn, worked with resellers and deputized other unknown companies to issue certificates in a “chain of trust” that now involves many hundreds of players, any of which may in fact be a weak link.