Council of Elrond

Can Tom cancel an attack from an agent (at a site in his regions)? I daresay no, as agents aren't hazards, is this correct? Thanks!

Agents played as hazards are hazards.
But agents (themselves) do not target anything.
So (short answer:) no.

Thanks, yes, I meant agents played as hazards. However, isn't an agent attacking a company targetting that company?

Agent's attack targets a company. But agent itself does not.
Similarly the action from Snowstorm - return a company to a site of origin - targets the company, but Snowstorm itself does not.

Tom Bombadil can tap to cancel the effects of one hazard that targets a company (of entity associated with the company).
Tom Bombadil cannot tap to cancel effects that target a company (of entity associated with the company) if they are not effects of hazard that targets the company (of entity associated with the company).