No, “this is a request for external resources” is not a good reason to close a question. That's not to say that a request for external resources is automatically on-topic, but the fact that a question can be interpreted as a request for external resources does not automatically make it off-topic. If a problem is best solved by applying an existing tool, so be it.
Questions like these have been found not to work on other sites (Stack Overflow and Programmers specifically)
(And Super User as well, but not Apple or Unix & Linux.) The reason why they didn't work isn't because these questions are intrinsically bad, but because the community of these sites has decided not to engage in the necessary moderation. Questions that call for existing tools require active moderation, with more quality enforcement than sites like SO and SU are willing to perform. On Software Recommendations, we've established guidelines for questions and answers, and we enforce them — we close questions and delete answers that don't meet our minimum requirements.
They attract spammy answer from people promoting their wares.
Some question types attract spam — for example, any question that mentions SSL certificates acts like dung to flies. That's not a reason to make all questions about SSL certificates off-topic on Webmasters.SE or Security.SE. On Software Recommendations, we systematically delete answers that just say “use this product its great”: answers must relate to the question specifically. If an answer demonstrates how the product solves the problem in the question, whether the answerer is affiliated with the product becomes moot.
The answers go out of date as technology changes.
That's no more true than for any other kind of question.
A problem like How do I identify spammers? is best solved by using existing tools and methodologies to recognize and suppress spam. The fact that some answers might recommend existing tools doesn't somehow make the question off-topic. As long as the question is about solving a specific problem, which this one is, it's fine.
Bad tool recommendation questions tend to be bad for reasons that are already covered by the standard close reasons. Too broad applies to questions that have requirements that are so general that a lot of methods would work and there isn't enough information in the question to prefer one method over another. Unclear applies to questions whose requirements are not precise enough. The two close reasons often overlap, so you even get to pick.
There is no need for a specific close reason. And there definitely should not be a blanket close reason that throws the baby with the bathwater.