This is an obvious one. I've dealt with a ton of recruiters over the years. If they're not willing to discuss a range upfront with you (amongst other things), they're lying to you. THERE IS NO JOB. They're just building their virtual rolodex for future sales.
If they want to grill you about what you do, who you know, references, etc. before revealing the name and location of the client... THERE IS NO JOB. (Hint for my younger colleagues: never reveal your references until you get an offer. They're just hitting you up for warm bodies that they can then probe.)
Recruiters do this to play some weird game of Glengarry Glen Ross, and I have no idea why. They swing in the extreme direction of sales and remove the technical aspects of it. We're treated like fodder for the job position sacrifice. And worse yet, a lot of them seem to think we're too stupid to know better.
I never expect a recruiter to be technical; they're a form of HR, not engineering. I wouldn't expect one to know how to read a TCP dump, or analyze a Nessus report for false positives. However a base understanding of what you're pushing for is to be expected. I had one recruiter almost shy away from me because he only saw a keyword listed once or twice on my resume...even though it's a core technology used in every single role I've done that's industry-wide.