Cato appears three times in NRH. Cato may be the embodiment of non-philosophic virtue, as conceived by Strauss. Here are the passages:

p. 168: By identifying traditional political philosophy with the idealistic tradition, Hobbes expresses, then, his tacit agreement with the idealistic view of the function or scope of political philosophy. Like Cicero before him, he sides with Cato against Carneades. 

That passage is explained by this later passage:

p. 196: The principle which was supposed to make possible a political doctrine of universal applicability, then, is not universally valid and therefore is useless in what, from Hobbes point of view, is the most important case-the extreme case. For how can one exclude the possibility that precisely in the extreme situation the exception will prevail.*

* Leviathan XIII and XV. One may state this difficulty also as follows: In the spirit of the dogmatism based on skepticism, Hobbes identified what the skeptic Carneades apparently regarded as the conclusive refutation of the claims raised on behalf of justice, with the only possible justification of these claims: the extreme situation-the situation of two shipwrecked men on a plank on which only one man can save himself-reveals not the impossibility of justice, but the basis of justice. Yet Carneades did not contend that in such a situation one is compelled to kill one's competitor (cf. Republic iii. 29-30): the extreme situation does not reveal a real necessity. 

Cato appears again in the Rousseau chapter:
p. 255: "Rousseau indicates the meaning of virtue clearly enough for his purpose by referring to the examples of the citizen-philosopher Socrates, Fabricius, and, above all, of Cato: Cato was the "greatest of men."*
* First Discourse, p. 59: Cato has given the human race the spectacle and model of the purest virtue which has ever existed.

At the end of the Rousseau chapter, here is what Strauss says:
p. 294: "As he confessed at the end of his career, no book attracted and profited him as much as the writings of Plutarch. The solitary dreamer still bowed to Plutarch's heroes," i.e. Cato.

And then again in Burke:
p. 318: "It is only a short step from this thought of Burke to the supersession of the distinction between good and bad by the distinction between the progressive and retrograde, or between what is and what is not in harmony with the historical process. We are here certainly at the pole opposite to Cato, who dared to espouse a lost cause."

Strauss himself, who espouses a lost cause, identifies to some extent with Cato (and Cicero), and with Cato (Cicero) against Carneades. Strauss agrees with the idea that "the extreme situation does not reveal a real necessity."